WHat numbers are compatible to 1/3, 1/4, 2/5?
What do you mean by "compatible to" ?
The product of the three numbers is 2/60 = 1/30
If you mean "what fractions can be reduced to those numbers because the denominator is evenly divisible by the numerator", compatible examples would be
1/3 = 3/9 = 5/15
1/4 = 7/28
2/5 = 6/15