The Trapezoid Midsegment Theorem states that a line segment connecting the midpoints of the legs of the trapezoid is parallel to the bases, and equal to half their sum.
In this problem you can see that 5x - 1 is the midsegment of the trapezoid, so using the rule:
solve:
2. Diagonals are congruent
You can see in this picture that the diagonals are not always congruent: