Solving a tax rate or interest rate problem using a system of linear equations

Question

Last year, Amanda had $30,000 to invest. She invested some of it in an account that paid 5% simple interest per year, and she invested the rest in an account that paid 6% simple interest per year. After one year, she received a total of $1,670 in interest. How much did she invest in each account?

Answer 1

X+Y=30000

0.05X+0.06Y=1670

solve: got one account X=13000 and account Y=17000