. We assume, that the number 260 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 260 is 100%, so we can write it down as 260=100%.
4. We know, that x is 6.75% of the output value, so we can write it down as x=6.75%.
5. Now we have two simple equations:
1) 260=100%
2) x=6.75%
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:
260/x=100%/6.75%
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 6.75% of 260

260/x=100/6.75
(260/x)*x=(100/6.75)*x - we multiply both sides of the equation by x
260=14.814814814815*x - we divide both sides of the equation by (14.814814814815) to get x
260/14.814814814815=x
17.55=x
x=17.55

now we have:
6.75% of 260=17.55