`A = 1/3 - 3/4 - (-3/5) + 1/72 - 2/9 - 1/36 + 1/15`
`= 1/3 - 3/4 + 3/5 + 1/72 - 2/9 - 1/36 + 1/15`
`= ( 1/3 + 3/5 + 1/15) - ( 3/4 - 1/72 + 2/9 + 1/36)`
`= (5/15 + 9/15 + 1/15) - ( 54/72 - 1/72 + 16/72 + 2/72)`
`= 1 - 71/72`
`= 72/72 - 71/72`
`= 1/72`
`#caty09`