`a) A = 1/3 - 3/4 - ( ( - 3 )/5 ) + 1/15 - 2/9 - 1/36`
`A = ( 1/3 - ( - 3 )/5 + 1/15 ) - ( 3/4 + 2/9 + 1/36 )`
`A = ( 5/15 - ( - 9 )/15 + 1/15 ) - ( 27/36 + 8/36 + 1/36 )`
`A = ( 14/15 + 1/15 ) - ( 35/36 + 1/36 )`
`A = 1 - 1`
`A = 0`
`b) 2/5 + ( - 4/3 ) - 1/2`
`= 12/30 + ( - 40/30 ) - 15/30`
`= ( - 28 )/30 - 15/30`
`= - 43/30`
`c) 1/3 - [ ( - 5/4 ) + ( 1/4 + 3/8 ) ]`
`= 1/3 - [ ( - 5 )/4 + 1/4 + 3/8 ]`
`= 1/3 - [ ( - 10 )/8 + 2/8 + 3/8 ]`
`= 1/3 - [ ( - 8 )/8 + 3/8 ]`
`= 1/3 - ( - 5 )/8`
`= 8/24 - ( - 15 )/24`
`= 23/24`
