to write 45/120 as a decimal you have to divide the numerator by the denominator of the fraction. we divide now 45 by 120 what we write down as 45/120 and get 0.375
Estimation is just giving a general answer to the situation and can be specified on specifics depending on the numbers used and whichever question it's asking. But also remember that whenever you estimate your answer will be an approximate answers, not an exact.
