We assume, that the number 80 is 100% - because it's the output value of the task. 2. We assume, that x is the value we are looking for. 3. If 80 is 100%, so we can write it down as 80=100%. 4. We know, that x is 12.5% of the output value, so we can write it down as x=12.5%. 5. Now we have two simple equations: 1) 80=100% 2) x=12.5% where left sides of both of them have the same units, and both right sides have the same units, so we can do something like that: 80/x=100%/12.5% 6. Now we just have to solve the simple equation, and we will get the solution we are looking for. 7. Solution for what is 12.5% of 80
80/x=100/12.5 (80/x)x=(100/12.5)x - we multiply both sides of the equation by x 80=8*x - we divide both sides of the equation by (8) to get x 80/8=x 10=x x=10
