help with math

Question

A combined total of $61,000 is invested in two bonds that pay 2% and 7% simple interest. The annual interest is $3,270.00. How much is invested in each bond? Solve the system with matrix.

What is 

The amount invested at 2% is $

The amount invested at 7% is $

Answer 1

a + b = 61,000 ---> a = 61,000 - b

0.02a + 0.07b = 3270

 

Substitute!

 

0.02(61,000 - b) + 0.07b = 3270

1220 - 0.02b + 0.07b = 3270

0.05b = 2050

a = 41,000

 

b = 61,000 - 41,000

b = 20,000