Question 147422
let x=4%
    y=5%

eq1 x+y=15000
    y=15000=x
eq2 .04x+.05(15000-x)=690

perform the indicated operations in the equation:
.04x+.05(15000-x)=690
.04x+750-.05x=690
.04x-.05x=690-750
.01x/.01=60/.01
x=6000

y=15000-6000=9000
therefore buddy invested 6000 at 4% and 9000 at 5%.
hope this other solution help you through...=)