How many terms are in this expression? -2x + 3y - 4

Two variables, x and y, vary inversely, and x=12 when y=4. what is the value of y when x=3?

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters

Carley bought a jacket that was discounted 10% off the original price. the expression below represents the discounted price in dollars, based on x, the original price of the jacket.