Since the area of a parallelogram is the base times it's height, we have (2x+1)(x+3)=42
2x^2+6x+x+3=42, 2x^2+7x=39, 2x^2+7x-39=0
x=3 or x=-13/2, yet x cannot equal to a negative number, so it x has to be equal to three(3).
Base of the parallelogram: 2(3)+1=7 units
Height of the parallelogram: 3+3=6 units