Question

earned $4200 and earned $174 in interest if one earns 3.5% and the other 4.5 % how much was invested at each rate

Answer 1

X + y = 4200 so x = 4200 - y
0.035x + 0.045y = 174

substitute x = 4200 - y into 0.035x + 0.045y = 174

0.035x + 0.045y = 174
0.035(4200 - y) + 0.045y = 174
147 - 0.035y + 0.045y = 174
0.01y = 27
y = 2700


x + y = 4200
x = 4200 - 2700
x = 1500

answer

$1500 in 3.5% 
$2700 in 4.5%