section 2.1/ 1*,3*,9,11*,12,15,18,23*, 27, 35*, 41

section 2.2/3*, 5, 15, (19-25 odd)*, 25, 39 (try not to look up the answer!)

section 2.3/ (1-25 odd)*, 31*, 32, 37, 45*, 53