Television sets. What does it mean to refer to a 20 inch TV set or a 25 inch TV set

Such units refer to the diagonal of the screen. A 35 inch TV set also has a width of 28 inches. What is the height in inches?
Please help, I have no clue as to how to figure this one out.
THANK YOU!!

In your question, 35" diag and 28"w, take the squarer root of sum of the two other sides squared.
Sorry, I gave you the wrong info, it should have been square the 35 and subtract the square of 28, then take sq root, answer would be 21"

the square of the diagonal is equal to the sum of the squares of the two sides(width and hieght)
so find the square of 35 and take away the square of 28 then the square root of the answer is
the hieght