Using the given information, we see that LOM + MON =LON. Now, we just substitute the expressions/numbers and simplify:
(2x+33)+(3x+20)=113
2x+33+3x+20=113
Simplify
5x+53=113
Collect like terms
5x=60
Divide by 5 on both sides to isolate x
x=12
Now we have found the value of x, we can find the value of MON.
MON = 2x+33
MON = 2(12)+33
MON = 24+33
MON = 67°