SAT Mathematics Practice Test 3

The linear equation $\mathit{y}=\mathit{k}\mathit{x}+4$ is in slope-intercept for, and so the slope of the line is $\mathit{k}$.
Since the line contains the point(c, d),the coordinates of this point satisfy the equation $\mathit{y}=\mathit{k}\mathit{x}+4;\mathit{d}=\mathit{k}\mathit{c}+4$.
Solving this equation for the slope k, gives $\mathit{k}=\frac{\mathit{d}-4}{\mathit{c}}$.
Choices B, C, and D are incorrect and may be the result of errors in substituting the coordinates of (c, d) in $\mathit{y}=\mathit{k}\mathit{x}+4$ or of errors in solving for k in the resulting equation.