There are two ways to do this but the way I prefer is to make one of the equations in terms of one variable and then 'plug this in' to the second equation. I will demonstrate
Look at equation 1,

this can quite easily be manipulated to show

.
Then because there is a y in the second equation (and both equations are simultaneous) we can 'plug in' our new equation where y is in the second one

which can then be solved for x since there is only one variable

and then with our x solution we can work out our y solution by using the equation we manipulated

.
So the solution to these equations is x=-2 when y=6
Answer is: B) An allowable amount of variation of a specified quantity, especially in the dimensions of a machine part.
Tolerance is how much something can take.
2x * 3x = 6x^2
2x * (-4) = 8x
7 * 3x = 21x
7 * (-4) = -28
6x^2 + 29x - 28
Divide and if u divide by 4 it would be 4/1 so the it the answer would be 4