Question #N484

If $y = 3x - 5$ and $x = 2y + 1$, what is the value of $x$?
A. -3
B. 1
C. 7
D. 13

Correct Answer is: C

We can solve this system of equations by substitution. Since we know that $x = 2y + 1$, we can substitute $2y + 1$ for $x$ in the equation $y = 3x - 5$. This gives us $y = 3(2y + 1) - 5$. Distributing the 3, we get $y = 6y + 3 - 5$. Combining like terms, we have $y = 6y - 2$. Subtracting $y$ from both sides, we get $0 = 5y - 2$. Adding 2 to both sides, we get $2 = 5y$. Dividing both sides by 5, we get $y = \frac{2}{5}$. Now we can substitute this value of $y$ back into the equation $x = 2y + 1$ to find $x$: $x = 2(\frac{2}{5}) + 1$, or $x = \frac{4}{5} + 1$, which simplifies to $x = \frac{9}{5}$. The value of $x$ is then $\frac{9}{5} \cdot \frac{5}{5} = \frac{45}{5} = 9$.