I did 2/3 + 1/3 I got 3/3.

Question

How do I do 7/15 + 9/20?
I'm not good at adding fraction with different denominators.

Answer 1

Your first problem is correct.

When you add fractions with different denominators, you need to find a common denominator.

One way to find this common denominator is to count by 15 and by 20 til you come to the first number that is divisible by both.

15, 30, 45, 60, 75, 90 . . .
20, 40, 60, 80, . . .

Since 60/15 = 4, multiply both the numerator and denominator by 4.

7/15 = 28/60
9/20 = 27/60

28/60 + 27/60 = 55/60 = 11/12

Answer 2

You make the denominator the same by finding a number that will divide both 15 and 20 evenly, then change the numerators to match.
(7/15) = (28/60)
(9/20) = (27/60)
Then you can add the numerators 28+27=55 and the denominator is 60 for 55/60. Now 5 will reduce both 55 and 60 to give 11/12. Check my work.

Answer 3

Thank You