The variables have to be substituted by the combinations of 0 and 1 and operate according to the previous table. The process is slow but infallible. It is not necessary to rush.

For example, to obtain the truth table of   we should design a table with 8 rows, from 000 to 111. For each of the rows we should proceed as 000:

The speed at which each one wants to proceed is free, but there will only be a correct result, one single logic result.