I need help with the even numbers!!!

Is each relation a function? if so, state whether it is one-to-one or many-to-one. 3. (-4,7), (-3,5), (1,4), (3,-8), (5,-11) 4. (-4,8), (-2,4), (0,1), (2,4), (4,8) 5. (-2, 1), (-2,3), (0,-3), (1,4), (3,1)

The sum of two numbers is 12 and their difference is 18 what are the two numbers

Evaluate cos2θ for cosθ = square root of 3/2