Please help don’t know how to do this I forget asap

The linear combination method is applied to a system of equations as shown. 4(.25x + .5y = 3.75) → x + 2y = 15 (4x – 8y = 12) → x – 2y = 3 2x = 18 what is the solution of the system of equations? (1,2) (3,9) (5,5) (9,3)

Solve each quadratic equation by factoring and using the zero product property. n^2 - 49 = 0

How can you find the mean absolute deviation (mad) for this set of data?