If his speed is 43 mph, then it takes him 40/43 of an hour to go 40 miles.
An hour = 60 minutes.
40/43 of 60 minutes = 55.8 minutes. He gets home 55.8 minutes after 6:24 PM.
Answer:
D. 10^10
Step-by-step explanation:
Multiplying numbers with exponents rule : 
explanation of rule : we simply keep the bases the same and add the exponents.
10^3 • 10^7
keep the base as 10 and add the exponents

Keep in mind that this only works when the bases are the same.
Y=4 because y is 4 all the time