Let’s suppose we have the equation ab=c. To find a in terms of b and c, we want a=? so to do this we divide both sides by b, which gives us a=c/b.
Now suppose we have a/b=c, then to find a we must multiply both sides by b: a=bc.
Each is a one-step solution.
The general rule is that we separate out the variable we need by “undoing” its operation on another constant or variable. Multiply is undone division and division is undone multiplication.