To get the solution, we are looking for, we need to point out what we know.
1. We assume, that the number 42 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 42 is 100%, so we can write it down as 42=100%. 4. We know, that x is 78% of the output value, so we can write it down as x=78%. 5. Now we have two simple equations: 1) 42=100% 2) x=78% 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: 42/x=100%/78% 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 78% of 42
42/x=100/78 (42/x)*x=(100/78)*x - we multiply both sides of the equation by x 42=1.28205128205*x - we divide both sides of the equation by (1.28205128205) to get x 42/1.28205128205=x 32.76=x x=32.76