Plz help ill give brainliest plzzz

An equation where variables are used to represent known values—function notation true or false

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.

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)