What is 54 feet by 10 legs and 20 arms?

Answer 1

The answer depends on what you are actually asking.

If you mean 54 ft x the length of 10 legs + the length of 20 arms, then you can express it as "54 ft x (the length of 10 legs + the length of 20 arms)".

If you know the actual length of each leg & each arm, then you could add the lengths of each leg & the lengths of each arm & and you could maken an expression such as: "54 ft x (TL leg ft + TL arm ft)

If you know the average leg length & average arm length, then you could maken an expression such as: "54 ft x (10 x aver leg len + 20 x aver arm len)

Lastly, if you know such lengths, you could multiple 54 x TL length of the appendage to arrive at total square feet number.