David and Marie had $300 altogether. After David spent 2/5 of his money and Marie spent $20, they each had the same amount of money. How much money did Marie have at first?

Answer 1

david --- x
Marie --- 300-x

David spent 2/5 of his money, so his has (3/5)x left
marie spent $20, so she has 300-x - 20 left

(3/5)x = 300-x-20
times 5
3x = 1400 - 5x
8x = 1400
x = 175, so
David had $175 and
Marie had 300-175 or $125

check:
David has 175 , he spends 2/5 of that or 70 , so he has 105 dollars left
Marie has 300-175 or 125 dollars, she spends 20, leaving her also with 105

Yeahhh!