11) First, add 74 and 43.
74+43=117
Subtract 117 from 180. Do this because this will give you the value of angle 1. This is because the sum of the angles in a triangle will always add up to 180 degrees.
180-117=63
Angle 1 = 63 degrees
Angle 2 also equals 63 degrees, because they are vertical angles.
Angle 2= 63 degrees
Now, add 63 and 79
63+79=142
Subtract 142 from 180
180-142=38
Angle 3 = 38 degrees
12)
First, subtract 56 from 180. Do this to find angle C. They are supplementary angles, so they will equal 180 degrees.
180-56=124
Angle C=124 degrees
Now, add 124 and 20
124+20=144
Finally, subtract 144 from 180
180-144=36
The measure of angle A is 36 degrees
Hope this helped! :)