Pls help its a grade

Dakota earned $7.50 in interest in account a and $18.75 in interest in account b after 15 months. if the simple interest rate is 4% for account a and 5% for account b, which account has the greater principal? explain. to make it a little easier, there is an image. good luck!

2x minus y equals 6, x plus y equals negative 3

Simplify the algebraic expression 8y-2(y+4)