Math
posted by John .
A woman invested $15,000, part at 7% annual interest and the rest at 8%. If she earned $1,100 in income over a oneyear period, how much did she invest at 7%?

Invested $P @ 7%.
Invested $(15,000P) @ 8%.
P*r*t + (15000P)*r*t = $1100.
P*0.07*1 + (15000P)*0.08*1 = 1100
0.07P + 1200 0.08P = 1100
0.01P = 11001200 = 100
P = $10,000 @ 7%.