Precisely Calculate Column Widths
We landed at an approximate value of 350px for the third column, which as you've seen isn't absolutely correct:
0:00 We landed on the approximate value of 350 pixels for this third column, which as you've seen is not absolutely correct, and it's now time to work out the precise value for that column. You can do some math in your head or on paper to work it out. Again, all the hints are right there in the HTML.