(5)^ -5 (5)^7
a. 1/25
b. 25
c. 10
d. 5 ^-35
To simplify this expression, we can use the rule of exponents that states when multiplying two numbers with the same base, we add the exponents.
So, (5)^-5 * (5)^7 = (5^(-5+7))
This simplifies to (5)^2 = 25.
Therefore, the answer is b. 25.