What is (7.2×10^2)(6×10^-7) in scientific notation?

Multiply the numbers on the left side of the multiplication sign. 

7.2 * 6 = 43.2

Combine the exponents attached to the 10s.

2 + (- 7) 
2 - 7
- 5

Your scientific notation should be 43.2 x 10⁻⁵.

As a way to check your

7.2 x 10² = 720 (move the decimal to the right twice)

6 x 10⁻⁷ = 0.0000006 (move the decimal to the left 7 times because it's a negative exponent)

Multiply the two together on a calculator, you get 0.000432. If you move the decimal 5 times to the left on 43.2 (again, because it's a negative exponent), you get 0.000432. The answers match.