How to solve for tax rate or interest rate

Question

Last year, Frank had
$20,000
to invest. He invested some of it in an account that paid
5%
simple interest per year, and he invested the rest in an account that paid
8%
simple interest per year. After one year, he received a total of
$1060
in interest. How much did he invest in each account?

Answer 1

Simultaneous equations:

 

x + y = 20,000, so x = 20000 - y

.05x + .08y = 1068

 

Substitute: (20000 - y).05 + .08y = 1068

Simplify: 1000 - .05y + .08y = 1068

              .03y = 68

              y = 2266.67

by subtraction, x = 17733.33