Question

1. you have some baseball trading cards. you give 21 baseball cards to a friend and have 9 left for yourself. how many baseball cards were in your original deck? write and solve an equation to find t, the number of baseball cards in your original deck.
2. model with math joy added 26 new contacts to her phone list. she now has a total of 100 contacts. let c represent how many contacts joy had on her phone list before she updated it. write an equation and solve for c.
3. reasoning jeremy bought a sandwich and a drink that cost him $7. his drink cost $1.75. solve the equation 7 = s + 1.75 to find s, the cost of jeremy’s sandwich.

Explanation:

Question 17

Step1: Define the equation

The original number of cards \( t \) minus the 21 given to a friend equals the 9 left. So the equation is \( t - 21 = 9 \).

Step2: Solve for \( t \)

Add 21 to both sides of the equation: \( t - 21 + 21 = 9 + 21 \), which simplifies to \( t = 30 \).

Step1: Define the equation

The original number of contacts \( c \) plus 26 new contacts equals 100. So the equation is \( c + 26 = 100 \).

Step2: Solve for \( c \)

Subtract 26 from both sides: \( c + 26 - 26 = 100 - 26 \), which gives \( c = 74 \).

Step1: Solve the equation \( 7 = s + 1.75 \)

Subtract 1.75 from both sides: \( 7 - 1.75 = s + 1.75 - 1.75 \).

Step2: Calculate the value

\( 7 - 1.75 = 5.25 \), so \( s = 5.25 \).

Answer:

The equation is \( t - 21 = 9 \) and the original number of baseball cards \( t \) is 30.

Question 18