For #19 part A :
By vertical angles and then same side interior angles 3x + 2x = 180
5x = 180
x = 36
For #19 part B:
You are correct with the 35, but you missed the fact that the 105 angle is supplementary with the unknown angle inside the triangle. So:
180 - 105 = 75
Then:
180 = 35 + 75 + x
180 = 110 + x
x = 70
Last question:
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