Canadian Math Contest

Question number 16.
The odd numbers from 5 to 21 are used to build a 3 by 3 magic square. (In a magic square, the numbers in each row, in each column, and the numbers on each diagonal have the same sum.) If 5, 9 and 17 are placed as shown what is the value of x?

when i first saw this question i thought to myself, "this question is doable, but its going to take a long time to figure out! there are so many different possibilities" But after thinking about it, with a couple of trial and errors i was able to figure it out.
First i wrote down all the odd digits from 5 to 21 and crossed out the digits that were already placed. Than i thought to myself "well if you want all the same sum, than the row with the lowest digit will probably be in the same row with the highest digit! Than i just continued to place the rest of the digits and it worked! :)
It was my first time doing the math contest, and i was very nervous!
but once i started, i began to relax a little and just tried to solve the problems one at a time. Towards the end, i began to feel pressed for time, and got a little fustrated with the questions that i could not solve.
Overall, i thought that the time limit was a little too short, but it was a good experience! I may have not done that well, but it was my first time, so i believe ill get better with practice ^^