I’m not sure about the answer to these 2 questions, pls provide a step by step explanation if possible, it’s ok if not

Answer:
2*10^4= 20000
Step-by-step explanation:
Divide 8.4 by 4.2 and multiply that by 10^7 divided by 10^3
8.4/4.2 = 2
10^7/10^3 =
10^4
Multiply them together:
2*10^4 = 20000