SAT Question 9ed4c1a2: Linear Equations In Two Variables answer and explanation with Desmos solution

In the xy-plane, the graph of an equation in the form $y=mx+b$, where $m$ and $b$ are constants, has a slope of $m$ and a y-intercept of $\left(0,b\right)$. Applying the distributive property to the right-hand side of the given equation yields $y=\frac{27}{4}x+\frac{15}{4}+7x$. Combining like terms yields $y=\frac{55}{4}x+\frac{15}{4}$. This equation is in the form $y=mx+b$, where $m=\frac{55}{4}$ and $b=\frac{15}{4}$. It follows that the slope of the graph of $y=\frac{1}{4}\left(27x+15\right)+7x$ in the xy-plane is $\frac{55}{4}$. Note that 55/4 and 13.75 are examples of ways to enter a correct answer.