Write a system of equations for each problem. Solve using the substitution method.

Question

A person invests $5000 in treasury notes and bonds. The notes pay 8% annual interest and the bonds pay 10% annual interest. If the annual income is $480, how much is invested in treasury notes?

Answer 1

n + b = 5000 -------> n = 5000 - b

.08n + .1b = 480 -----> 8n + 10b = 48,000

 

8(5000 - b) + 10b = 48,000

40,000 - 8b + 10b = 48,000

2b = 8000

b = 4000

 

n = 5000 - 4000 = 1000