Question 1125909
<pre>  
The triangle and the two given exterior angles are
drawn below and are indicated in <b><font color="green">green</font></b> by the two 
<b><font color="green">green</font></b> arcs. 

All you need to do is to calculate the two interior angles 
indicated by the <b><font color="red">red</font></b> arcs.

{{{drawing(400,280,0,20,-5,9,

line(0,0,5,0), red(triangle(5,0,15,0,7.5,4.330127019)),
line(15,0,20,0),
green(arc(5,0,3,-3,60,180),locate(3,2,"120°")),
green(arc(15,0,3,-3,0,150),locate(15.7,2,"150°")),
red(arc(5,0,3.4,-3.4,0,60),locate(6.5,1.4,"??°")),
red(arc(15,0,3.4,-3.4,150,180),locate(12,.9,"??°"))
 )}}}

Edwin</pre>