## Geometry: Common Core (15th Edition)

$x = \frac{5}{3}$
Parallelograms have opposite sides that are congruent. In order for $ABCD$ to be a parallelogram, we must have $AD$ and $BC$ equal to one another. $AD = BC$ Let's plug in what we are given in the diagram: $3x + 1 = 6x - 4$ Subtract $1$ from each side of the equation to isolate variables to one side of the equation: $3x = 6x - 5$ Subtract $6x$ from each side of the equation to isolate the variable to the left side of the equation: $-3x = -5$ Divide each side of the equation by $-3$ to solve for $x$: $x = \frac{5}{3}$