Answer:
24 (units)
Explanation:
Because Quadrilateral EFGH is being dilated by a scale factor of 3/4, this means that each side of E'F'G'H' gets multiplied by 3/4. In this case, we are going to divide by 3/4 to return to the original figure (or multiply by 4/3 since that is the reciprocal)
This means that side HE is 18/(3/4) = 18(4/3) = 72/3 = 24 units