To solve this equation, we can combine the logarithms on the left side using the properties of logarithms.

log2(5x-7) - log2(5) = log2(21)
log2((5x-7)/5) = log2(21)

Now, since the bases of the logarithms are the same, we can drop the logs and set the expressions inside the parentheses equal to each other:

(5x-7)/5 = 21

Now, we can solve for x:

5x - 7 = 105
5x = 112
x = 112/5
x = 22.4

Therefore, the solution to the equation is x = 22.4.