To use the substitution method we need to convert one equation in terms of a certain variable and substitute this equation to the other equation. For this case we are asked to substitute the first equation to x in the second equation. Therefore, the equation to substitute is:
<span>-x - 2y = -4
</span>x = 4 - 2y
Okay so plug them in to get x and y so use 5 as x and 1 as y
For number 80 the answer is 15.
Neither A nor B because there is an input value that repeats for both tables.