A) `5/3` + ( 7 + `-5/3`)
= `5/3` + 7 + `-5/3`
= (`5/3` + `-5/3`) + 7
= 0 + 7
= 7
B) `-7/31` + ( `24/17` + `7/31` )
= `-7/31` + `24/17` + `7/31`
= (`-7/31` + `7/31`) + `24/7`
= 0 + `24/17`
= `24/17`
C) ( `3/1` + `1/5` ) + `-3/7`
= ( `15/5` + `1/5` ) + `-3/7`
= `14/5` + `-3/7`
= `98/35` + `-15/35`
= `83/35`
#NOCOPY
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