SAT Mathematics Practice Test 2

Multiplying each side of $\mathit{x}+\mathit{y}=0$ by 2 gives $2\mathit{x}+2\mathit{y}=0$.Then, adding the corresponding sides of $2\mathit{x}+2\mathit{y}=0$ and $3\mathit{x}-2\mathit{y}=10$ gives $5\mathit{x}=10$.Dividing each side of $5\mathit{x}=10$ by gives $\mathit{x}=2$ ,Finally,substituting 2 for x in $\mathit{x}+\mathit{y}=0$ gives $2+\mathit{y}=0$, or $\mathit{y}=-2$ Therefore, the solution to the given system of equations is $\left(2,-2\right)$.
Alternatively the equation $\mathit{x}+\mathit{y}=0$ can be rewritten as x = −y, and substituting for $-\mathit{y}$ in $3\mathit{x}-2\mathit{y}=10$ gives $5\mathit{x}=10$, or $\mathit{x}=2$. The value of y can then be found in the same way as before.
Choices A, C, and D are incorrect because when the given values of x and y are substituted into $\mathit{x}+\mathit{y}=0$ and $3\mathit{x}-2\mathit{y}=10$, either one or both of the equations are not true. These answers may result from sign errors or other computational errors