Question 1037897
<pre><b>
This one IS drawn to scale! :)  Measure the angles and see!

{{{drawing(300,7800/29,-3,26,-3,23,
red(arc(0,0,10,-10,0,42),arc(31cos(42*pi/180),31sin(42*pi/180),12,-12,222,259),
arc(19.00544935,0,8,-8,79,180)),
triangle(0,0,19.00544935,0,31cos(42*pi/180),31sin(42*pi/180)),
locate(0,0,A), locate(19,0,B), locate(23.6,21.3,C),locate(6.2,10,b=31),
locate(2,1.75,"42°"), locate(20.1,18,"37°"), locate(8,0,"c=?"),
locate(21,10,"a=?"), locate(17,2,"?°") 

  )}}}  

First we find angle B:

    A + B + C = 180°
42° + B + 37° = 180°
      79° + B = 180°
            B = 101°

Use the law of sines:

{{{a/sin(A)}}}{{{""=""}}}{{{b/sin(B)}}}{{{""=""}}}{{{c/sin(C)}}}

{{{a/sin("42°")}}}{{{""=""}}}{{{31/sin("101°")}}}{{{""=""}}}{{{c/sin("37°")}}}

Taking the first two:

{{{a/sin("42°")}}}{{{""=""}}}{{{31/sin("101°")}}}

{{{a}}}{{{""=""}}}{{{31sin("42°")/sin("101°")}}}

{{{a}}}{{{""=""}}}{{{31sin("42°")/sin("101°")}}}

{{{a}}}{{{""=""}}}{{{21.13129011}}}

Taking the last two:

{{{31/sin("101°")}}}{{{""=""}}}{{{c/sin("37°")}}}

{{{(31sin("37°"))/sin("101°")}}}{{{""=""}}}{{{c}}}

{{{19.00544935}}}{{{""=""}}}{{{c}}}

You can round to nearest tenth!  :)

Edwin</pre></b>