Linear equations in two variables SAT question

The correct answer is $\frac{18}{11}$. For a line that passes through the points $(x_1,y_1)$ and $(x_2,y_2)$ in the xy-plane, the slope of the line can be calculated using the slope formula, $m=\frac{y_2-y_1}{x_2-x_1}$. It's given that a line passes through the points $(4,6)$ and $(15,24)$ in the xy-plane. Substituting $(4,6)$ for $(x_1,y_1)$ and $(15,24)$ for $(x_2,y_2)$ in the slope formula, $m=\frac{y_2-y_1}{x_2-x_1}$, yields $m=\frac{24-6}{15-4}$, or $m=\frac{18}{11}$. Therefore, the slope of the line is $\frac{18}{11}$. Note that 18/11 and 1.636 are examples of ways to enter a correct answer.