Billy and Oscar had $645. Billy spent
38 of his money on a laptop. Oscar spent
13 of his money on a notebook. The laptop cost $108 more than the notebook. How much money had Billy left?
| |
Billy |
Oscar |
Total |
Before |
8 u |
+ 288 |
3x3 =
9 u |
645 |
Change |
- 3 u |
- 108 |
- 1x3 =
- 3 u |
|
Comparing the laptop
and the notebook |
108 more |
|
|
After |
5 u |
+ 180 |
2x3 =
6 u |
|
108 ÷ 3 = 36
5 x 36 = 180
8 x 36 = 288
Total amount that Billy and Oscar had at first
= 8 u + 288 + 9 u
= 17 u + 288
17 u + 288 = 645
17 u = 645 - 288
17 u = 357
1 u = 357 ÷ 17 = 21
Amount that Billy had left
= 5 u + 180
= 5 x 21 + 180
= 105 + 180
= $285
Answer(s): $285
