Angles on a straight line add up to 180&deg;.<br><br>
&bull; MNO is a straight line<br>
&bull; Read the given angle on the straight line from the diagram<br>
&bull; Angle r plus the given angle = 180&deg;<br>
&bull; Angle r = 180&deg; − 135&deg; = 45&deg;<br><br>
Final Answer: 45