How do you find the equivalent exponential expression ##(7^3)^2##?

See explanation.

When you want to evaluate an expression containing a power of another power you write it as one power with exponent equal to product of all exponents in the original expression:

##a^(b^c)=a^(bxxc)##

So in the given example:

##(7^3)^2=7^(3xx2)=7^6##