Question 96019
x = amount invested at 10%
9000 - x = amount invested at 7%
.10x + .07(9000-x) = 780
.10x + 630 - .07x = 780
.03x + 630 = 780
.03x = 150
x = 5000
9000 - 5000 = 4000
so $5000 was invested at 10%
$4000 was invested at 7%
:)