Twenty five subtracted from a number is -90. How would I write this as an equation?

Which statement best describes the polynomial

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

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?