What do you call a triangle whose two sides sum to equal the third side?

Write two subtraction equations that are equivalent to 5 + 12 = 17.

Suppose that a households monthly water bill (in dollars) is a linear function of the amount of water the household uses (in hundreds of cubic feet, hcf). when graphed, the function gives a line with slope of 1.65. if the monthly cost for 13 hcf is $46.10 what is the monthly cost for 19 hcf?

Ineed the solution to this problem and the steps.