Using the points (2, 15) and (7, 21), what is the best estimate of what the mean cost of an oil change willbe car for Sadie's car when it is 12 years old?

What is the y-intercept of the line with the equation 3x + 4y = 12?

What is the equivalent fraction for the following fraction using 5 as the multiplier? 1/2

If the angle bisectors of a pair of opposite angles of a quadrilateral are the opposite sides of a parallelogram formed by the two angle bisectors and two sides of the quadrilateral, is the quadrilateral always a parallelogram? explain your answer.