SATMathematics Practice Test 1

Adding x and $19$ to both sides of $2\mathit{y}-\mathit{x}=-19$ gives x = 2y + 19.
Then, substituting $2\mathit{y}+19$ for x in $3\mathit{x}+4\mathit{y}=-23$ gives $3\left(2\mathit{y}+19\right)+4\mathit{y}=-23$ .
This last equation is equivalent to $10\mathit{y}+57=-23$ .Solving $10\mathit{y}+57=-23$ gives $\mathit{y}=-8$ .
Finally, substituting $-8$for y in $2\mathit{y}-\mathit{x}=-19$ gives $2\left(-8\right)-\mathit{x}=-19$ , or $\mathit{x}=3$ .
Therefore, the solution (x, y) to the given system of equations is $\left(3,-8\right)$ .

Choices A, C, and D are incorrect because when the given values of x and y are substituted in $2\mathit{y}-\mathit{x}=-19$ , the value of the left side of the equation does not equal $-19$ .