These videos might help you
https://www.khanacademy.org/math/algebra/systems-of-linear-equations/systems-of-linear-equations-wor...
Answer:
Divide 12 by 6........................D
For a system of equations such as this, add both of the equations together. The d values will cancel each other out, making 2e=-4. This means that e=-2. If you plug this into one of the equations, you will have d + (-2) = 1. Isolate the variable by adding -2 to both sides: d=3. Written in the format described above (d,e), your answer is (3, -2).
Distribute on both sides
2x - 8 = 6x + 12
Move x to one side
-20 = 4x
Divide by 4
-5 = x
