I like to use this equation:
(Percent) * (total) = (part)
In this case, your total is 125, because it is the bigger number. 55 is the part, because it is a small part of that 125. to find the percent, you have to rearrange this equation so it looks like:
so when we plug in the values it looks like:

to that math and the answer will give you:
0.44
turn this answer into a percent by multiplying by 100:
0.44 * 100 = 44%