math
posted by Edna .
Mrs. Jones is building a deck behind her house. Top 28 ft; Right 25 ft; Bottom 4 ft. What is the length of the unlabeled Left side of this deck?
Ans. 7 ft.
Book's explanation: 〖25〗^2〖24〗^2=625576=49=7
Where did they get 24 from? Thank you for your help!

I can't picture the deck. Top? Bottom?
All I can say is that 24 = 284, the difference between top and bottom.
But the 7^2+24^2=25^2 seems to be for the legs and diagonal of a triangle. Oh, well, maybe you have a diagram in front of you. 
New tile is being laid on a floor that is 12 ft. long and 9 ft. wide. Each square tile measures 9 inches on each side. How many tiles will be needed?
Ans. 192
Please tell me how they got 192
Thank you.
PS digressing
how do I sent you diagrams, i.g., triangle diagram of a deck?