Why do stores offer sales such as buy one, get one at half price or buy two, get one free

What is the value of x in the equation7x+2y=48 when y=3

What are the interpretations of the line 3x - 15y = 60? x-intercept y-interception a: x 20 - y -4 b: x 5 - y 20 c: x -3 - y 15 d: x -4 - y 20

The length of a rectangle plus its width is 24 cm. the area is 143 square cm. what are the length and width of the rectangle?