Highschool college-prep math. I need some help on this and if you do would will be greatly appreciated.

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

Enter numbers to write 0.000328 0.000328 in scientific notation. 1 1 0.000328=3.28 × 0 . 000328 = 3 . 28 × =3.28×10 = 3 . 28 × 10

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. how many hours after the truck's departure will the two meet?