TRIAL AND ERROR
What do you think what is trial and error?
Our electronic definitions web site has answer for that as well:
trial and error
suppose you have a problem involving two simultaneous equations. Instead of solving this in the usual left-brain mathematical way, you can guess an answer and then calculate all the unknowns. One of the calculated unknowns is the very answer that you guessed. You compare the calculated and guessed answers to see how different they are. Then you guess another answer that will close the gap between the guessed and calculated answers. After several trials, the gap becomes small enough that you have an approximate answer