**Example 1**:

The straight lines MN and PQ in the diagram above are parallel. Find the value of

*q*.

*Solution:*If two lines are parallel, their gradients are equal.

*m*

_{1}=

*m*

_{2}

*m*

_{MN}=

*m*

_{PQ}

60 = 6

*q*+ 306

*q*= 30*q*= 5