Question

Air is 20.9% oxygen by volume.How many mL of air contains 175 mL of oxygen?

Answer 1

So lets say we have 100 mL of air then this will contain 20.9 mL oxygen.

Thus 100 mL/20.9 of air will contain
1 mL of oxygen.

So how many mL of air contain 150 mL of oxygen?