
Explanation:
Step 1:
The total of the angles in any triangle is 180°.
So to determine the third angle of the given triangles, we subtract the sum of the other two sides from, 180°.
The third angle = 180° - (the first angle + the second angle).
Step 2:
For triangle ABC,
,

So

For triangle DEF,
,

So

Step 3:
For triangle GHI,
,

So

For triangle JKL,
,

So
