On Monday, Erika, Raeann, Risa and Tiffany spent a total of $123. On Tuesday, Erika spent twice of what she spent on Monday, Raeann spent the same as what she spent on Monday, Risa spent $15 less than what she spent on Monday, and Tiffany spent $12 more than what she spent on Monday. All of them spent an equal amount on Tuesday. How much did Erika and Tiffany spend altogether on Monday?
| |
Erika |
Raeann |
Risa |
Tiffany |
Total |
| Before |
1 u |
3 u |
3 u + $15 |
3 u - $12 |
$123 |
| Change |
x 3 |
|
- $15 |
+ $12 |
|
| After |
3 u |
3 u |
3 u |
3 u |
|
Total amount that the four girls spent on Monday
= 1 u + 3 u + 3 u + 15 + 3 u - 12
= 10 u + 15 - 12
= 10 u + 3
10 u + 3 = 123
10 u = 123 - 3
10 u = 120
1 u = 120 ÷ 10 = 12
Total amount that Erika and Tiffany spent on Monday
= 1 u + 3 u - 12
= 4 u - 12
= 4 x 12 - 12
= 48 - 12
= $36
Answer(s): $36
