In numerals, fifty-two is written as 52 and one hundred seventy-two is written as 172. Now, one hundred seventy-two minus fifty-two means subtracting 52 from 172, i.e. 172 - 52 = 120. Using number names 100 to 200 chart, 120 in words is written as:

⇒ 100 + 20 = One hundred + twenty = One hundred twenty.