12% of 120 =?

12% of 120 = 0.12 * 120 = 14.4
When doing these problems, wherever you see the word "of" replace it with a multiply sign, and wherever you see the word "is" replace it with an equal sign. For example, "What is 20% of 100?" you would write "N = 20% * 100"

100%<----->120

10%<------->12
1%<-------->1.2

10%<------>12
2%<-------> 2.4

12%<------>14.4

14.4

120 x 12%
= 120 x 12/100
= 120 x 3/25
= 360/25
= 14.4

Whenever you are asked to find a percentage of a number, they are basically telling you to divide the percentage by 100 and multiply it by the number. In your case it would be:
12/100 * 120 = 14.4

14.4