Question 178471
White vinegar is available as a 5% acetic acid solution and a 10% acetic solution, by volume. How many millilitres of each solution must be mixed to make 100mL of a 7% solution. 
I tried: Let x represent the amount of 5% vinegar.
Let y represent the amount of 10% vinegar. 
These are the 2 equations I came up with, but my answer came out wrong.
x+y=100
100=x(0.05)+y(0.01) 
The correct answer is supposed to be 60mL of 5% solution and 40mL of 10% solution. 

:
x+y=100....eq 1
.05x+.1y=.07(100)
:
you were oh.........so close you forgot to multiply the final 100 ml solution by
:
7% and it should be .1y not .01y
:
I will let you carry it from here.