The formula of slope is
.
The line 1 passes through the points
.
Substitute the values of
in the above formula.
.
The line 2 passes through the points
.
Substitute the values of
in the above formula.
.
If two lines are parallel then their slopes are equal.
\Therefore
.

Multiply each side by negative 7.
\

Subtract 2 from each side.
\
.
The value of
.