Plz help, it’s been due for a long time but I needed help.

How is working backward similar to solving an equation?

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)

Aquadratic equation in standard from is written ax^2= bx+c, where a, b and c are real numbers and a is not zero?