SAT Question 0d1dca87: Systems of Linear Equations answer and explanation with Desmos solution

Since it's given that $x=2$, the value of $y$ can be found by substituting $2$ for $x$ in the first equation and solving for $y$. Substituting $2$ for $x$ yields $3\times 2+y=29$, or $6+y=29$. Subtracting $6$ from both sides of this equation yields $y=23$.