Question 348330
Let x = the number of pints of water to be mixed with the 3 pints of 90% developer to obtain (3+x) pints of the 17% developer mixture.
3(0.9) = (3+x))(0.17) Simplify.
2.7 = 0.51+0.17x Subtract 0.51 from both sides.
2.19 = 0.17x Divide both sides by 0.17
12.8824 = x
Yuo need to mix 12.9 pints of water with the 3 pints of 90% developer mixture to obtain (12.9+3 = 15.9) pints of 17% developer mixture.