-12 = f/0.2
First, we can start out by making our goal to get the variable (f) on one side of the problem by itself. To do this, multiply both sides by 0.2.
[tex]-12 \times 0.2 = f[/tex]
Second, our next step is to multiply -12 times 0.2. This can be solved in your head, on a piece of paper, on a calculator, etc. (-12 times 0.2 = 2.4).
[tex]-2.4 = f[/tex]
Third, our last step will be to switch sides. Basically flip the problem.
[tex]f = -2.4[/tex]
Answer: [tex]\fbox {x = -2.4}[/tex]