Answer:
<MON= 59°
Explanation:
Look at the diagram what is <LON? It is the angle of the whole line. Remember when any three letters come the middle letter is the angle like here if it is asking MON it is requesting the angle O between the lines M and N. The angle between the line L and M is given so to find <MON we can simply minus <LOM with the total angle (<LON)
<MON= <LON - <LOM
= 142-83
<MON= 59°