Answer:
5:7
Explanation:
One way is to
divide both terms by the greatest common factor (GCF), 3:
15 ÷ 3 = 5
21 ÷ 3 = 7
So it would be 5:7.
Another way is to simplify the numbers, so
15 simplified is 5
21 simplified is 7
So it would be 5:7.
Super sorry but couldn't find another one :C.