2/3=40/60
1/2=30\60
3/4=45/60
1/6=10/60
4/15=16/60
7/20=21/60
11/30=22/60
в) -8 + ( + 9 ) = 1
г) + 8 + ( - 9 ) = -1
д) + 12 + ( - 15 ) = - 3
е) - 13 + ( + 18 ) = 5
ж) - 2 + ( + 18 ) = 16
з) + 25 + ( - 32 ) = - 7