over (a number)

In writing or formal speeches, you use "over" to mean "more than" some number:

There must have been over a thousand people there.

Over 20% of our employees have Master's degrees or Ph.D.'s.

Over 500 people have signed up to volunteer.

It's used in both spoken and written English, but in writing it's probably more common than using "more than".

miles

A mile is a measurement of distance that's used in the United States. It's equal to about 1.61 kilometers.

(some number) per (something)

Use "___ per ___" to talk about a ratio, which is the relationship between numbers. For example:

I earned fifty dollars per day.

We made two per person.

The speed limit is 35 miles per hour.

(a driver) is doing (a speed)

This is a casual way to talk about how fast someone's driving, expecially when they're driving fast:

I was only doing maybe 70 or 71 but the cops pulled me over.