Answer:
C. 1.2x
Step-by-step explanation:
He pays 1 x for his haircut, and an additional 20% on top of that, or an additional 0.2x. If you write that as an expression, you can simplify it like this:
You can also work it out by multiplying by 1.2 as stated in answer C. If his haircut costs $10, adding a 20% tip of $2 is the same as multiplying by 1.2.