18 18 1 5 15 − 1 5 4 15 1 30 + 30 7 3 2 = + + - - + = = = 24 24 1 5 6 1 + 60 1 60 15 3 1 2 − 2 15 1 = = + + = - - 40 1 40 7 60 1 + 90 1 60 2 - 5 90 = = + + - = - = 3 20 1 20 - 1 15 15 2 1 + 24 24 7 1 60 - 60 5 = - = + = + = - - ( 15 24 ) ( 20 6 ) ( 14 16 ) = ( 18 20 ) ( 12 15 ) ( 16 25 ) = ( 36 40 ) ( 18 50 ) ( 35 20 ) = |