Answer: 15mL
<u>Step-by-step explanation:</u>
Create a table. Multiply across and add down. The bottom row (Mixture) creates the equation.
<u> Qty </u> × <u> % </u> = <u> Total </u>
Solution A 10 15% → 0.15 10(0.15) = 1.5
<u>Solution B x 20% → 0.20 x(0.20) = 0.20x</u>
Mixture 10 + x × 18% → 0.18 = 1.5 + 0.20x
(10 + x)(0.18) = 1.5 + 0.20x
1.8 + 0.18x = 1.5 + 0.20x
1.8 = 1.5 + 0.02x
0.3 = 0.02x
15 = x