The length of GH is equal to the sum of FG, BC, and 1.
Additional details such as a scale factor or the lengths of corresponding sides in the parallelograms are needed to calculate the length.
The original question cannot be answered accurately as there is not enough information to determine the length of GH in the parallelogram EFGH.
For a parallelogram ABCD that is similar to parallelogram EFGH, one would typically use the properties of similar figures and a scale factor to determine the corresponding side lengths.
Without the scale factor or the lengths of corresponding sides in either parallelogram, it is not possible to determine the length of GH directly from the information given.
BC/FG = AD/EH
21/7 = AD/EH
AD = 3EH
GH = FG + EH = (FG + BC) + (AD) = FG + BC + 3EH
GH = FG + BC + 3(EH) = FG + BC + 3(7/21) = FG + BC + 3(1/3)
GH = FG + BC + 1