Question 979584
Area of a parallelogram is bh
(3x+1)(x+1)=40
3x^2+4x+1=40
3x^2+4x-39=0

(3x+13)(x-3)=0
x=3, -(13/4), and the second is impossible.

base is 3x+1=10 units
height is 3+1=4 units