Hello from MrBillDoesMath!
Answer:
240 is one common denominator.
(Not asked for by problem but least common denominator is 120)
Discussion:
A common denominator (one of many) is given by multiplying the denominators: 5, 8, and 6. That is 5*8*6 = 240 is a common denominator.
If the least common denominator is desired, then that is 5 * 8 * 3 = 120
(we use 3 as 6 = 2*3 but 2 is already accounted for in the factorization of 8)
Thank you,
MrB