Algebra question

Question

A scientist has two solutions, which she has labeled Solution A and Solution B. Each contains salt. She knows that Solution A is 40% salt and Solution B is 90% salt. She wants to obtain 150 ounces of a mixture that is 60% salt. How many ounces of each solution should she use?

Answer 1

(x oz)(40%) + (150 oz - x oz)(90%) = (150 oz)(60%)

(x)(0.40) + (150 - x)(0.90) = (150)(0.60)

0.4x + 135 - 0.9x = 90

-0.5x = -45

x = 90 oz of the 40% soln (A) + 60 oz of the 90% soln (B)