Answer
Let x = the number of ounces of Solution A 
Let y = the number of ounces of Solution B 
x + y = 180 y = 180 - x 
.60x + .85y = .75(180) 
.60x + .85y = 135 Multiply both sides of the equation by 100 to remove the decimal points. 
60x + 85y = 13500 
60x + 85(180 - x) = 13500 
60x + 15300 - 85x = 13500 
-25x = -1800 
x = 72ounces 
y = 180 - 72 
y = 108 ounces