Answer :
common factors are numbers that all the numbers in question can be divided by and the result will be an integer.
Factors of 15 are 1,3,5 and 15
Factors of 45 are 1,3,5,9,15,45
Factors of 90 are 1,2,3,5,6,9,10,15,18, 30,45,90
So common factors (that they all have) are 1,3,5 and 15
Factors of 15 are 1,3,5 and 15
Factors of 45 are 1,3,5,9,15,45
Factors of 90 are 1,2,3,5,6,9,10,15,18, 30,45,90
So common factors (that they all have) are 1,3,5 and 15
Factors of 15: 1,3,5 and 15. Factors of 45: 1,3,5,9,15,45.
Factors of 90: 1,2,3,5,6,9,10,15,18, 30,45,90.
So common factors for all of them are 1,3,5 and 15
Factors of 90: 1,2,3,5,6,9,10,15,18, 30,45,90.
So common factors for all of them are 1,3,5 and 15
