Need help!! don't know what I'm doing

In a graph with several intervals o data how does a constant interval appear? what type of scenario produces a constant interval?

The lengths of two sides of a right triangle are given. find the length of the third side. round to the nearest tenth if necessary. a) y = 12/5x + 39/5 b) y = 5/12x + 5/39 c) y = 12/5x - 39/5 d) y = 5/12x - 5/39

Based on the diagrams, what is the value of x?