Question 662333
x+y = 3600
.07x + .03y = 172
substitute into the second equation
.07(3600 - y) + .03y = 172
252 - .07y + .03y = 172
252 - 172 = .04y
80 = .04y
y = $2000 at 3%
x = 3600 - 2000 = $1600 at 7%
Proof
.07(1600) + .03(2000)
112 + 60 = 172