1) Let's start with the angle "a"
∠a is vertical opposite to the angle that measures 35º. Vertical opposite angles are congruent.
So ∠a=35º
2)
∠a and ∠b are the acute angles of a right triangle. The acute inner angles of a right angle are complementary angles, which means that they add up to 90º
Then:
So ∠b=55º
3)
Finally, ∠c is a linear pair with the angle that measures 70º, this means that they are supplementary.
From this expression, you can calculate the value of ∠c
So ∠c=110º