Sue got a lot of money for graduation from a mysterious, rich aunt that she’d never known she had. Her first thought was AUDIO EQUIPMENT, but then she figured she really ought to put it away for a rainy day. She divided it into two parts. One part had $250 more than the other part. She invested the smaller part at 6% interest, and the larger part at 8%. A year later, the total interest she had accumulated was $72.50. How much money did she get from her mysterious, rich aunt for graduation in the first place?
0.06x + 0.08x + $20 = $72.50
0.14x = $52.50
x = $375
We can see that the first part was $375 and we can find the second part by substitution.
(x + $250) = $375 + $250 = $625