Question 250370
                        3%solution + 7%solution = 4%solution
amount of solution(ml)  x + y = 75 OR x=75-y     
amount of acid (ml)    .03x + .07y  = 0.04(75)
.03(75-y)+.07y=3
2.25-.03y+.07y=3
.04y=3-2.25
.04y=.75
y=.75/.04
y=18.75 ml of 7% solution is used.
x+18.75=75
x=75-18.75
x=56.25 ml. of 3% solution is used.
Proof:
.03*56.25+.07*18.75=.04*75
1.6875+1.3125=3
3=3