#3**+1 **

"y" = 180 - 131 = 49° = the vertical angle to y at the bottom left of the top triangle

The angle supplemental to the 142° angle = 180 - 142 = 38°

So "w" = 180 - 49 - 38 = 93°

By the interior angle theorem, the angle at the bottom right of the top triangle = 93 - 42 = 51°

So.. "t" will = 180 - 49 - 51 = 80°

CPhill Oct 2, 2018