Question

If $7x+4y=18$ and $3x+y=3$, what is the value of $x+y$?

• A. $\frac{27}{5}$
• B. $11$
• C. $12$
• D. $14$
• E. $15$

Answer 1

Answer: (A)

$\frac{27}{5}$

Let $7x+4y=18...\left(1\right)$
$3x+y=3...\left(2\right)$

Multiplying equation $\left(2\right)$ with $4$ we get, $12x+4y=12...\left(3\right)$

Subtracting equations $1$ from $3$, we get $5x=-6\Rightarrow x=\frac{-6}{5}$

Substituting $x=\frac{-6}{5}$ in the equation $\left(2\right)$, we get $3\left(\frac{-6}{5}\right)+y=3$

$\Rightarrow y=3+\frac{18}{5}=\frac{15+18}{5}=\frac{33}{5}$

Now, $x+y=\frac{-6}{5}+\frac{33}{5}=\frac{27}{5}$