Lisa Chen invested $24,000, part at 8% and the rest at 7.2%. How much did she invest at each rate if her income from the 8% investment is two thirds that of the 7.2% investment?

Answer 1

part invested at 8% ---- x
part invested at 7.2% -- 24000-x)

income from first = .08x
income from 2nd = .072(24000-x)

.08x = (2/3)(.072)(24000-x)
.24x = .144(24000-x)
.24x = 3456 - .144x
.384x=3456
x = 9000

so $9000 invested at 8%
and $15000 invested at 7.2%