Math problem help

I need help with this math problem.

Prepare 1/4 scalp cleanser using 50mL water as the solvent and medicinal shampoo. What is the total volume?

What is the medicinal shampoo volume?

The book answer is total volume: 66.7 and Medicinal shampoo volume is 16.7. Please show me how to work this because my answer was totally different from the book.

If it's 1/4 scalp cleanser, then it's 3/4 of water.

You know that you're using 50mL of water.....so that's 3/4 of your volume. You need to figure out how much 1/4 is. So, 50 / 3 = 16.6666667 or 16.7. If you add that to the water (50mL from the problem) the total volume is 66.7mL

Thank you!