A speck of dust is 5.0 x 10-7 m wide. Which of the following is the best way to rewrite this quantity, using more appropriate units?
A. 5.0 x 10^-7 m
B. 5.0 x 10^-4 mm
C. 5.0 x 10^-5 cm
D. 5.010^-10 km

HELP PLEASE

Elena and her husband marc both drive to work. elena's car has a current mileage (total distance driven) of 15,000 and she drives 23,000 miles more each year. marc's car has a current mileage of 46,000 and he drives 9,000 miles more each year. will the mileages for the two cars ever be equal? explain.

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

1mile equals approximately 1.6 kilometers. which best approximates the number of miles in 6 kilometers?