Question

irene is making lemonade. the recipe calls for 18 cups of lemon juice. irene already added 3 cups of lemon juice. how many more cups of lemon juice does she need to add?
$3 + c$
$18 - c = 3$
$18 = c + 3$
diagram with 3 and c adding to 18
diagram with three cs adding to 18
$18 + c = 3$

Explanation:

Step1: Define variable

Let \( c \) = cups of juice still needed.

Step2: Set up correct equation

Total needed = added + needed: \( 18 = c + 3 \)

Step3: Verify matching model

The bar model with 3 and \( c \) summing to 18 matches this equation.

Answer:

Correct options:

• \( 18 = c + 3 \)
• The bar model with two segments labeled 3 and \( c \) summing to 18

To solve for \( c \):

Step4: Rearrange to solve for c

\( c = 18 - 3 \)

Step5: Calculate final value

\( c = 15 \)

Final number of cups needed: 15