a) 25⁰30' + 13⁰18' - 10⁰11' = 25⁰30' + 3⁰7' = 28⁰ 37'
b)180⁰ - 120⁰40'30'' + 15⁰10'20'' = 195⁰10'20'' - 120⁰40'30'' =
= 194⁰70'20'' - 120⁰40'30'' = 194⁰69'80'' - 120⁰40'30'' = 74⁰29'50''
c) 40⁰15'2'' x 3 = 120⁰45'6''
d) 51⁰10' x 2 = 102⁰20'
e) 28⁰20'28'' : 2 = 14⁰10'14''