`a ) 3/{x - 7} = 27/135`
`3/{x - 7} = 3/15`
`x - 7 = 15`
`x = 15 + 7`
`x = 22`
`b ) x - ( 2/3 + 2/15 + 2/35 + 2/63 ) = 1/9`
`x - ( 2/{1 × 3} + 2/{3 × 5} + 2/{5 × 7} + 2/{7 × 9} ) = 1/9`
`x - ( 1 - 1/3 + 1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 ) = 1/9`
`x - ( 1 - 1/9 ) = 1/9`
`x - 8/9 = 1/9`
`x = 1/9 + 8/9`
`x = 9/9 = 1`
`#dtkc`