Did two of them for you as reference for the rest.
Explanation for #1
The sum of all the angles in a triangle is 180. Simply add the given angles. Take 180 and subtract the sum of the given angles
180 - (58 + 47) = 75
Missing angle is 75
Explanation for #4
A straight angle is 180 degrees. Same thing as the first: add the given angles then take 180 and subtract it.
Then take 180 <em>again </em>and subtract the answer you got from the first step.
180 - (21 + 34) = 125
180 - 125 = 55
The missing angle is 55
