`a, 5/9 : (1/11 - 5/22)+ 5/9 : (1/15 - 2/3)`
`= 5/9 : (2/22 - 5/22) + 5/9 : (1/15 - 10/15)`
`= 5/9 : (-3)/22 + 5/9 : (-3)/5`
`= 5/9 . (-22)/3 + 5/9 . (-5)/3`
`= 5/9 . (-22 /3 - 5/3)`
`= 5/9 . (-9)`
`= -5`
`b, (1+1/2+1/4+1/8+1/16)/(1-1/2+1/4-1/8+1/16)`
`= (16/16+8/16+4/16+2/16+1/16)/(16/16-8/16+4/16-2/16+1/16)`
`= (31/16)/(11/16)`
`= 31/11`
`c, (5-5/3+5/9-5/27)/(8-8/3+8/9-8/27):(15-15/11+15/121)/(16-16/11+16/121)`
`= (5(1-1/3+1/9-1/27))/(8(1-1/3+1/9-1/27)):(15(1-1/11+1/121))/(16(1-1/11+1/121))`
`= 5/8 : 15/16`
`= 2/3`