Question

1. read each story problem. identify the unknown quantity, and write the addition or subtraction expression that is described. finally, evaluate your expression using the information given in column four.

story problem	description with units	expression	evaluate the expression if:	show your work and evaluate

( 7 + 2 )
9
sammy has 9 baseballs. |

ella wrote 8 more stories than anna in the fifth grade.

let ( a ) represent the number of stories anna wrote

anna wrote 10 stories in the fifth grade.

( a = 10 ) | |

lisa has been dancing for 3 more years than danika.

let ( d ) represent the number of years danika danced for

danika has been dancing for 6 years.

( d = 6 ) | |

the new york rangers scored 2 fewer goals than the buffalo sabres last night.	let		the rangers scored 3 goals last night.
george has gone camping 3 times fewer than dave.	let		george has gone camping 8 times.

1. if george went camping 15 times, how could you figure out how many times dave went camping?

eureka math
lesson 18: writing and evaluating expressions—addition and subtraction

Explanation:

Problem 1 (Ella wrote 8 more stories than Anna...)

Step1: Define the unknown and expression

Let \( a \) be Anna's stories. Ella's stories: \( a + 8 \).

Step2: Substitute \( a = 10 \)

\( 10 + 8 = 18 \)

Step1: Define unknown and expression

Let \( d \) be Danika's years. Lisa's years: \( d + 3 \).

Step2: Substitute \( d = 6 \)

\( 6 + 3 = 9 \)

Step1: Define unknown and expression

Let \( s \) be Sabres' goals. Rangers' goals: \( s - 2 \).

Step2: Substitute \( s = 3 + 2 = 5 \)? Wait, no—Rangers scored 3, so Sabres: \( 3 + 2 = 5 \), Rangers: \( 5 - 2 = 3 \). Wait, expression: Let \( s \) = Sabres’ goals, Rangers: \( s - 2 \). Given Rangers = 3, so \( s - 2 = 3 \Rightarrow s = 5 \), but evaluation of Rangers’ goals is 3. Wait, the problem says "evaluate the expression if: The Rangers scored 3 goals". Wait, maybe expression for Rangers: \( s - 2 \), and we need to find Sabres? No, the story is Rangers scored 2 fewer than Sabres. So Rangers’ goals: \( s - 2 \), where \( s \) is Sabres’ goals. If Rangers scored 3, then \( s - 2 = 3 \Rightarrow s = 5 \), but the expression for Rangers is \( s - 2 \), evaluation: 3 (matches). Wait, maybe the expression is for Rangers: let \( s \) = Sabres’ goals, Rangers: \( s - 2 \). So expression: \( s - 2 \), evaluate when Rangers = 3? Wait, no, the table column: "Evaluate the Expression if: The Rangers scored 3 goals". So the expression is for Rangers’ goals: \( s - 2 \), but we need to define \( s \) as Sabres’ goals. Wait, maybe I misread. Let's re-express: Let \( s \) = Sabres’ goals. Rangers’ goals: \( s - 2 \). Given Rangers scored 3, so \( s - 2 = 3 \Rightarrow s = 5 \), but the evaluation is for Rangers’ goals, which is 3. So expression: \( s - 2 \), evaluation: 3 (since Rangers scored 3). Wait, maybe the unknown is Sabres’ goals, but the story is about Rangers. Let's correct: Let \( r \) = Rangers’ goals, \( s \) = Sabres’ goals. Then \( r = s - 2 \). Given \( r = 3 \), so \( 3 = s - 2 \Rightarrow s = 5 \). But the expression should be for Rangers: \( s - 2 \), so when evaluating, we know \( r = 3 \), so the expression \( s - 2 = 3 \), but maybe the expression is \( s - 2 \) with \( s = 5 \), so \( 5 - 2 = 3 \). So steps:

Step1: Define \( s \) = Sabres’ goals, Rangers: \( s - 2 \).

Step2: Since Rangers = 3, \( s = 3 + 2 = 5 \). Substitute into expression: \( 5 - 2 = 3 \).

Answer:

Expression: \( a + 8 \), Evaluation: 18 (Ella wrote 18 stories)

Problem 1 (Lisa has been dancing... )