a) 23° 45' + 15° 20' ×4=23° 45' + 60° 80'=83° 125' =85° 5'
b) 35°17' ×5 - 67° 35'=175°85' - 67° 35'=108°50'
c) 7×12° 15' +3× 12°15'=10×12° 15'=120°150'=122°30'
d) 1° +2° +.......10°=10°×11°:2=55°
e) 5°+ 6° +..........15°=1°+2°+3°+4°+5°+6°+...+15°-(1°+2°+3°+4°)=
=15°×16°:2-4°×5°:2=120°-10°=110°
f) 75° : 5=15
g) 28° 64' :4=7°16'
h) 127°43': 3