Helen practiced the piano 5 days last week. The list below shows the number of minutes she practiced each day: 20, 25, 30, 20, 30

What is the MAD (mean absolute deviation) in Helen's practice times?

The number of revolutions of two pulleys is inversely proportional to their diameters. if a 24-inch diameter pulley making 400 revolutions per minute is belted to an 8-inch diameter pulley, find the number of revolutions per minute of the smaller pulley.

Find the solution of this system of equation -7x+y=-20 9x-3y=36

X2 + y 2 = 36 x + y = 6 solve the system of equations.