Explanation:
Hey there!
HCF stands for highest common factor. When you are asked about to find the HCF of any number find the factors and take common from all the factors of the numbers.
The given numbers are: 15,30,90.
15 = 3*5
30 = 2*3*5
90 = 2*3*3*5
Now, from the above solutions take all the common factors.
From the factors of all three numbers, 3*5 are common.
Therefore, the HCF of the numbers is 3*5 = 15.
Hope it helps!