`a ) 5/7 + 3/5 `
`= 25/35 + 21/35 `
`= 46/35`
`b ) 8 3/7 - ( 2 2/3 + 5 2/7 )`
`= 8 3/7 - 2 2/3 - 5 2/7`
`= ( 8 3/7 - 5 2/7 ) - 2 2/3`
`= 3 1/7 - 8/3`
`= 22/7 - 8/3`
`= 10/21`
`c ) 7/5 . ( - 19 )/15 + 7/5 . ( - 3 )/15 - 7/5 . 8/15`
`= 7/5 . ( ( - 19 )/15 + ( - 3 )/15 - 8/15 ) `
`= 7/5 . ( - 2 )`
`= ( - 14 )/5`
`d ) 50% - 2 1/2 . 2021^0 + ( 0,5 ) : 1/4`
`= 1/2 - 5/2 . 1 + 1/2 : 1/4`
`= 1/2 - 5/2 + 2`
`= - 2 + 2`
`= 0`