Question 84145
.18X+.08(21000-X)=1980
.18X+1680-.08X=1980
.1X=1980-1680
.1X=300
X=300/.1
X=3000 AMOUNT INVESTED @ 18%.
PROOF
.18*3000+.08(21000-3000)=1980
540+.08(18000)=1980
540+1440=1980
1980=1980