Slope-Intercept Form
Slope-intercept form is a way of writing equations that looks like this:

Usually, we use slope-intercept form for linear equations, where y is the dependent variable and x is the independent variable.
m is the slope of the line and b is the y-intercept, but this is irrelevant for this question.
Solving the Question

Because we need to make m the independent variable, we must isolate n on one side of the equation.

Answer
