One possible answer is:
5((7x3)-6).
Explanation:
75 ends in 5, so it is divisible by 5. 75/5 = 15. If we can arrange 7, 6 and 3 some way to make 15, we can use this multiplied by 5.
7x3=21, and 21-6=15; this gives us what we need!
5(21-6) = 75; 21 = 3x7, so 5((3x7)-6).
