Regina's teacher recently gave her a homework assignment on solving equations. Since she has been thinking about saving for a new cell phone,
she decided to use the assignment as an opportunity to model a savings plan
She created this equation to model the situation. In it, yrepresents the total amount saved for the new cell phone, 74 is the amount of money
she has now, 40 is the amount of money she saves each month for the phone, and xrepresents the number of months since she started saving
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 purchase the new cell phone. Review her
work, and select the error.
Justification
74 + 40x=y
74 + 40x-74-y-74
40x=y=74
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
401
1: given
2: subtraction property of equality
3: simplification
4: multiplication property of equality
5: simplification
6: substitution, y=834
7: simplification
- 74
40 =
40
- 74
40
x=
Step 6:
Step 7:
10