Relations and Triangles

Given the triangle at the right,

Cut the three angles from the triangle

Line the angles beside each other on the next slide

The three angles will form a line

The sum of the angles equal

 $43\degree\ +\ 32\degree\ +105\degree\ =\ 180\degree$  

 $m\angle A=180\degree-\left(30\degree+96\degree\right)$  

 $m\angle A=180\degree-126\degree$  

 $m\angle A=54\degree$