Rebecca had 9 10 of a yard of ribbon. Then she gave 7 20 of a yard to a friend. How much does she have left?

Answer 1

Assuming that "9 10" & "7 20" refers to 9/10 & 7/20:

Rebecca originally had 9/10 of a yard of ribbon, but then Rebecca gives 7/20 of a yard to a friend. In order to find how much ribbon Rebecca has left, we have to subtract 7/20 from the original 9/10.

HOWEVER, we need the denominators (the bottom of the fraction; the 10 & 20) to be the same according to the rules of fractions. We will multiply 9/10 by 2/2 so that the denominator (10) matches the denominator of the other fraction (20); shown like this: 9/10 x 2/2 = 18/20

Now we just work our subtraction magic! Now that both denominators are the same, we can subtract 7/20 from the original 18/20 (remember that 18/20 is the same as 9/10). ALSO, when it comes to adding & subtracting fractions, it is only the nominators (the top of the fraction; the 18 & 7) that are affected; shown like this: 18/20 - 7/20 = 11/20

So Rebecca has 11/20 of a yard of a ribbon! Hope that helps.