`a) 7/3 : 14/15 - 9/4`
` = 7/3 . 15/14 - 9/4`
` = 5/2 - 9/4`
` = 1/4`
`b) 15 3/7 - (8/9 + 7 3 /7)`
` = 15 + 3/7 - (8/9 + 7 + 3/7)`
` = 15 + 3/7 - 8/9 - 7 - 3/7`
` = (15-7) + (3/7 - 3/7) - 8/9`
` = 8 - 8/9`
` = 64/9`
`c) |-5/12|+ (-2/3)^2 . (20%-1/2)`
` = 5/12 + 4/9 . (1/5-1/2)`
` = 5/12 + 4/9 . (-3/10)`
` = 5/12 + (-2)/15`
` = 17/60`
`d) 5/9 . 7/13 - 30/23 + 6/9 . 5/13 + 7/23`
` = (5/9 . 7/13 + 6/9 . 5/13) - (30/23 - 7/23)`
` = ((5.7)/(9.13) + (6.5)/(9.13)) - 1`
` = (5.7 + 6.5) / (9.13) - 1`
`= 5/9 - 1`
` = -4/9`
