The triangle formed is aright angled triangle with the right angle between the length and width of the paper cut hence the diagonal represents the hypotenuse side.
Recall that Pythagoras theorem states that
a^2 + b^2 = c^2 where c is the hypotenuse side and a, b are the opposite and adjacent sides
The width of the rectangular bathroom tile is 11 and 2/3 centimeters. Taft is because 2x5 is 10 cm and 1/3x5 is 5/3. 5/3 simplified as a mixed number is 1 and 2/3. 1 and 2/3 combined with 10 is 11 and 2/3 centimeters.