You have the next quadrilateral:
The side AB has a negative slope, it means that the inclination is to the left
The side BC has a possitive slope, it means that the inclination is to the right
In a parallelogram you have opposite sides with the same measure, then you can say that:
Being m the slope:
[tex]\text{mAB}=\text{mDC}[/tex][tex]\text{mAD}=\text{mBC}[/tex]Then the slope of AD is: 7/2[tex]\text{mAD}=\text{mBC}=\frac{7}{2}[/tex]
