HCF of 75, 120, 290 by long division

Answer 1

I guess you want to use long division to find the prime factors of each number. Go ahead, and you will find that
75 = 3 * 5^2
120 = 2^3 * 3 * 5
290 = 2 * 5 * 29
So, the highest common factor is just 5
No other factor appears in all three numbers.