Question

Tracy received a $21.00 gift card for phone apps. She has used $9.00 of the value and wants to buy one more app from the list shown to use up the balance. Complete the bar diagram and use the equation $21.00 = x + $9.00 to determine which app she should buy.

Answer 1

Let x be the amount left on the card. From 21 = x + 9,

x = 21 − 9 = 12.

Bar diagram: a bar of length 21 split into two parts: one part labeled $9 (used) and the other labeled $12 (remaining).

So she should buy the $12 app.