Final answer:
The measure of side U'V' is 13.5 units.
Step-by-step explanation:
To find the measure of side U'V', we need to apply the given scale factor of 3/4 to the original length of side UV. Since the scale factor is less than 1, the length of U'V' will be smaller than 18. We can find U'V' by multiplying the original length by the scale factor:
U'V' = (3/4) * 18 = 13.5
Therefore, the measure of side U'V' is 13.5.