Alberto and Betty went out for lunch. Originally, Alberto had more money than Betty did by 20%.
After Alberto and Betty spent $37 and $18, respectively, Betty has more money than Alberto does by 20%.
How much money in total do they have left after lunch?
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Let A = Alberto's money and B= Betty's money.
1 . 2 = 5 6 = B A = A − 3 7 B − 1 8
Suppose A = 6 x and B = 5 x for some x.
Then 6 ( 6 x − 3 7 ) = 5 ( 5 x − 1 8 ) .
3 6 x − 2 2 2 = 2 5 x − 9 0
1 1 x = 1 3 2 ; x = 1 2 .
The remaining money = 1 3 2 − 3 7 − 1 8 = 7 7 .