Regina's teacher recently gave her a homework assignment on solving equations. Since she has been ti she decided to use the assignment as an opportunity to model a savings plan.
She created this equation to model the situation. In it, y represents the total amount saved for the new
she has now, 40 is the amount of money she saves each month for the phone, and x represents the num
a regular amount:
74 + 40x=y.
She then solved the equation to determine how many months she'd need to save to have enough to pur
work, and select the error.
Justification
1: given
2: subtraction property of equality
3: simplification
4: multiplication property of equality
5: simplification
6: substitution, y = 834
7: simplification
Step 1:
Step 2:
Step 3:
Step 4:
74 + 40x=y
74 + 40x - 74 = y- 74
40x = y-74
40.5 y - 74
40 =
40
y - 74
X= 40
834 - 74
X = 40
Step 5:
Step 6: