Which relation is not a function?

Combine like terms to make a simpler expression 3z+z

If f(x) = 4x - 3 and g(x) = x + 4, find (f - g) (x)

Examine this system of equations. what integer should the second equation be multiplied by so that when the two equations are added together, the x term is eliminated? 3/4x+1/7y=6 1/8x-3/5y=16