Parallelograms have opposite sides that are equal, so you can set BC and AD equal to each other to find the value of x if the figure is a parallelogram. x + 3 = 2x - 1 3 = x - 1 4 = x
Now check 4 + 3 = 2(4) - 1 7 = 7
The value of x that makes ABCD a parallelogram is x = 4.