Answer:
The first expression, (5^2*x^6*y^(-7))(5*x^0*y^28)
Explanation:
Basically, add up the exponents for each unique base. We have two exponents with bases of 5 in this expression, 5^2 and 5 (which is equal to 5^1). Add the exponents together to get 3, so you have 5^3 = 125.
Add up the exponents for bases of x this time. We have x^6 and x^0. 6 + 0 = 6, so we have x^6.
Finally add up the exponents for bases of y. We have y^28 + y^(-7) = 28 + (-7) = 21, so we have y^21.