Let be the amount invested in the account with 4%. Therefore is invested in the account with 8%

These totals are equal to $760. So we add them to give:

Solve for n which will be the answer to part a. To find the answer to part b subtract the value of n from 11,000

Therefore $3,000 is invested at 4% and $8,000 is invested at 8%

I am not 100% sure about the position of n regarding the power. In this case it's not important for the power 1 doesn't change anything