What is (abc)^2?
What if the question had been [(a^2)*(b^3)*c]^4?
I think the operating rule is how to deal with a power raised to another power, instead of the multiplication of the same base raised to two different powers. That says
(x^y)^z = x^(y*z)
...or we multiply the two exponents to get the final simplified power of x (because there's z copies of x^y getting multiplied together). Using numbers, (x^3)^4 would simplify to x^(3*4) = x^12.
Excellent answer Mona. Another way to think about this is that (abc)^2 = aabbcc
abc is being used as a factor twice therefore according to the laws of exponents when we are multiplying exponents we add them. In this case abc times abc would be a^2b^2c^2. abcxabc each variable is raised to the first power so 1+1 equals 2 and therefore the exponent is equal to 2 and you do this for each variable.