So supplementary angles are ones that add up to 180degrees and complementary ones add up to 90degrees.
So for the left side, you find what angle is supplementary to the given one. For the angle of 35, another angle of 145 will add up to 180.
The right side want you to find the complementary angles, so for the angle of 18, another angle of 72 will add up to 90.
I always forget supplementary vs complementary, but a little bit of practice will help a lot.