Word problem help

Question

A nurse mixes 490cc of a 40% saline solution with a 10% saline solution to produce a 25% saline solution. How much of the 10% solution should he use?

This is the question I'm stuck on. I don't even know how to set it up. I looked up videos but I'm still stuck. Please help!

Answer 1

% saline gives you volume of saline essentially, so

(40%)490 + (10%)X = (25%)(490+X)

X is the unknown volume. 490+X because you are mixing the two volumes together.