Simplify as much as possible. [2(x^-2)(x^4/5)(y^6) / x+y ]^-3

Last year, laura had $30,000 to invest. she invested some of it in an account that paid 7% simple interest per year, and she invested the rest in an account that paid 8% simple interest per year. after one year, she received a total of $2230 in interest. how much did she invest in each account?