Me with number 6 the one on the side is 16 it got cut off

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)

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?

Let f(x) = 5/x and g(x)=2x2+5x. what two numbers are not in the domain of f o g