Apply the property of negative integer exponents to rewrite 7^(-3) * 7^(-5) as an expression with positive exponents only.

7^(-3) * 7^(-5) = _

To rewrite 7^(-3) * 7^(-5) with positive exponents only, we use the property of negative integer exponents, which states that a^(-n) = 1 / (a^n).

Using this property, we get:

7^(-3) * 7^(-5) = 1 / (7^3) * 1 / (7^5)

Now, we use the property of exponents that states that when dividing two numbers with the same base, we subtract the exponents:

1 / (7^3) * 1 / (7^5) = 1 / (7^(3+5))

Simplifying the exponent, we get:

1 / (7^(8))

So, 7^(-3) * 7^(-5) is equal to 1 / (7^(8)).