Question 1055098

let the investment be $x 

$x at 10% interest is x(1+0.1) = 1.1x

$(90+3x)  at 8% interest = 1.08 (90 +3x) = 97.2 + 3.24x 

if the total amount he receives by the end of the year is 798.38 , then:

1.1x + 97.2 + 3.24x = 798.38 
4.34x  = 798.38 - 97.2
4.34x = 701.18

x = 162
 
(now substitute the value of x )
1.1 x 162= $178 at 10 % interest rate
97.2 + 3.24(162) = $622  at 8% interest rate