math
posted by Tonya on .
becca received some money for her birthday. she spent 2/5 then she spent 1/2 the she spent 2/3 and had $15 left . how much did you receive for her birthday

To do this, you have to work backwards. That is, starting from the $15 left. Note that she spent 2/3 of her money and had $15 left. Therefore, this $15 is actually 1/3 of the money she had:
1/3 of something = 15
To do this, just divide 15 by 1/3:
15 / (1/3) = 15*3/1 = $45
And then she spent 1/2. This means that the other half is actually $45:
1/2 of something = 45
Divide:
45 / (1/2) = 45*2 / 1 = $90
And finally, she spent 2/5 of the original money, and had $90 left. Thus this $90 is actually 3/5 of her money:
3/5 of something = 90
Divide:
90 / (3/5) = 90*5/3 = $150 (original amount of money)
Hope this helps~ :)