Question

(2 x 10^4) x (2 x 10^3)

Answer 1

10's to a certain power is basically the amount of zeros after the 1. So like 10^5 means that there are 5 zeros after the one, making the answer 100,000. In this case, 2x10^4 is (2x1)+(4 zeros after) x (2x1)+(3 zeros after)
To solve this expression, you just multiply 2x2=4 and add the "zeros after" which results to "7 zeros after".
Answer: 40,000,000

Answer 2

4,000,000,000