Answer:
20x
Explanation:
1) Identify commonalities in the numbers at hand (x + 40 divisible by 1, 2, 4, 5, 8, 10, 20, 40 and 60 divisible by 1,2,3,4,5,6,10,12,15,20,30,60) overlap is x and 1,2,4,5,10,20) 20 is the highest factor and x is the only factor.
2) put them together GCF: 20x