`a ) {5 + 5/3 + 5/9 + 5/27}/{8 + 8/3 + 8/9 + 8/27}`
`= {5 + 5 × 1/3 + 5 × 1/9 + 5 × 1/27}/{8 + 8 × 1/3 + 8 × 1/9 + 8 × 1/27}`
`= {5 × ( 1 + 1/3 + 1/9 + 1/27 )}/{8 × ( 1 + 1/3 + 1/9 + 1/27 )}`
`= 5/8`
`b ) {2/5 + 2/15 + 2/20 + 2/25}/{3/7 + 3/21 + 3/28 + 3/35}`
`= {2/5 + 2/5 × 1/3 + 2/5 × 1/4 + 2/5 × 1/5}/{3/7 × 1/3 + 3/7 × 1/4 + 3/7 × 1/5}`
`= {2/5 × ( 1 + 1/3 + 1/4 + 1/5 )}/{3/7 × ( 1 + 1/3 + 1/4 + 1/5 )}`
`= 2/5 : 3/7`
`= 14/15`
`#dtkc`