Final answer:
The length of side S'T' in the dilated figure with a scale factor of 3 is 54 feet, which is calculated by multiplying the original length of ST (18 feet) by the scale factor.
Step-by-step explanation:
The length of side ST in polygon STUV is 18 feet. To find the length of side S'T' in the dilated figure S'T'U'V', where the scale factor is 3, we multiply the original length by the scale factor.
Length of S'T' = Length of ST × Scale Factor
Length of S'T' = 18 feet × 3 = 54 feet.
Therefore, the correct answer to the question is 54 feet, which means the option c) 54 feet is the right choice.