Find the angle between the given vectors to the nearest tenth of a degree.

u = < 6, -1> , v = < 7, -4>
can someone explain how to do this?

7x+8y=-18, 4x-9y=-3 solve the system of equations

Alicense plate is to consist of 44 digits followed by 55 uppercase letters. determine the number of different license plates possible if the first and second digits must be? odd, and repetition is not permitted.

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).