Question 553917
I don't have your book, so I have no idea what "41 and 42" are.
But below are four examples of two supplementary angles. 
They form a linear pair.  The sum of their measures is 180°:


{{{drawing(200,100,-1,1,0,1, line(-1,0,1,0), line(0,0,3,7) )}}}   {{{drawing(200,100,-1,1,0,1, line(-1,0,1,0), line(0,0,0,5) )}}}   {{{drawing(200,100,-1,1,0,1, line(-1,0,1,0), line(0,0,10,1,7) )}}}   {{{drawing(200,100,-1,1,0,1, line(-1,0,1,0), line(0,0,-5,5) )}}}

Edwin</pre>