find the value of x so that AB and DC are parallel

According to the properties of a parallelogram, the consecutive interior angles are supplementary, this is that the sum of its measures is 180.
Use the expressions given for 2 of the consecutive angles to find the value of x. Remember, the sum of these expressions must be 180.
[tex]\begin{gathered} (3x+15)+(7x+25)=180 \\ 10x+40=180 \\ 10x=140 \\ x=\frac{140}{10} \\ x=14 \end{gathered}[/tex]x has a value of 14.