If by square feel you mean square feet, and the rectangle is 10ft by 14ft, you simply multiply 10 by 14 to get 140, and then add the extension ft2, so the answer is 140ft2.
A 30ft x 14ft room = 420 square feet.
154
it is 980sq ft
10 ft * 8 ft = 80 sq ft = 7.432 sq metres (to 3 dp).
18 ft * 10 ft = 180 sq ft = 16.72 sq metres (approx)
140
A 30ft x 14ft room = 420 square feet.
6.096 meters
14*14 = 196 square feet
154
10 feet x 10 feet = 100 square feet.
Yes, this shed if constructed properly will stay standing for many years.
You will need 140 tiles (10 x 14 = 140)
Two squares.
16
120
it is 980sq ft