Answer:
speed = 4 mph
Explanation:
The best way to do this is to convert the fractions into decimals.
2/5 = 0.4 miles
1/10 = 0.1 hours
Answer: speed = 0.4 /0.1 = 4 miles per hour.
Put this into your calculator
.4
÷
.1
=
The answer should come out as 4.
You can do this with fractions but it will drive you a little batty.

Notice that the second set of fractions multiplys 2/5 * 10/1. That's because you invert and multiply the bottom fraction.