Answer:
[tex]\huge\boxed{a =\frac{s-t}{m-r}}[/tex]
Step-by-step explanation:
In order to convert an equation to solve for another variable, we need to algebraically manipulate the problem until we're left with a isolated on one side.
Step 1: Subtract [tex]t[/tex] from both sides
Step 2: Divide both sides by [tex]m- r[/tex]
Hope this helped!