Find the inner product for (4,8) × (6,-3) and state wheter the vectors are perpendicular

Pls! does anybody know a shortcut for answering these types of questions in the future?

`if you have a set of parallel lines a and b cut by transversal x, if angle 1 = 167 degrees, what is angle 4 and why. also what is the measure of angle 5 and why? you need to use the names of the angle relationship and explain. ''.

What is the gcf of 20c^3-5c^4+30c^6