The answer is C = 3 If we substitute 3 into the x values in each equation we can see that the top and bottom is the same value and both sides are also the same value, meaning that it is a parallelogram;
Top and bottom of parallelogram:
2x + 3 2 (3) + 3 = 6 + 3 = 9
And
x + 6 (3) + 6 = 9
And then the two sides; 6x - 5 6 (3) - 5 = 18 - 5 = 13
And
4x + 1 4 (3) + 1 = 12 + 1 = 13
There are two pairs of equal sides which shows that this is a parallelogram.
