Answer:
$7800
Explanation:
The total interest earned can be found by summing the earnings from each of the investments.
Setup
Let x represent the total amount invested. Then Jessica's earnings are ...
(x/2)(0.07) +(x/2)(0.13) = 780
Solution
Simplifying the equation gives ...
(x/2)(0.07 +0.13) = 780
0.10x = 780
x = 7800 . . . . . . . . divide by 0.10
Jessica has $7800 invested.