The number of isomers of C₇H₁₆ ???

i know hw to get the ans by the conventional method but is there any shortcuts or shortcut formulas for finding the no.of. isomers in alkanes , alkenes & alkynes???

Pls... help me now

Pls i will approve the ans anyway help me aieee approaching n givin me the spine chills !!!

'x' gm of a compound A3B2C5 contains 'y' gm of A atoms

 

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how to represent the possible fischer projections for 2-bromohexane