I'm not sure if I'll explain this correctly but I'll try. So basically, pretend the question was log (base 10) 100=x. In this case, you would look at it as if it was, 10^x=100 in which case, x=2. Sometimes, looking at the variables is confusing. In your problem, a = log (base 7) b^7, the problem is 7^a=b^7. So I guess the answer would just be b^7. Is that the answer? You pretty much take the base, raise to whatever it equals and then set that equal to the number next to the log.
