1 function {(2,2),(4,4),(6,6),(8,8)} written is a function the other following coordinates are not functions due to it not being a straight line as a 'proper' function should be.
Um... it'll take each pipe 80 mins, bcz if together they take that long, then to find the pipes time separately, you just multiply it by two to show it doing the work the other pipe did as well. Is that what you wanted??
The length of side b is 52 because using the Pythagorean theorem we know that a² + b² = c². When we plug in the known values we would get 1521 + b² = 4225, and when we subtract 1521 from both sides we would get b = 52.