Here is your answer:
5.3 × 10^4 × 4.2 × 10^3
5.3 × 4.2 = 22.26
4 + 3 = 7
= (22.26 × 10^7) or option B.
When doing questions like these you will have to multiply the two numbers on the left of the multiplication sign which in this case is 5.3 and 4.2 which would equal 22.26 but then you have to add the exponents in this case it would be 4 and 3 and would equal 7 which through all would equal 22.26 × 10^7 or option B.
Hope this helps!
