Angles on a straight line sum to 180&deg;.<br><br>Let &angle;MON = 1 unit. Then &angle;JON = 3 units.<br>From the figure, &angle;JON + &angle;MON = 120&deg;.<br>4 units = 120&deg;, so 1 unit = 30&deg;.<br><br>Final Answer: 30&deg;