self doubt

Question

please explain whithout  drawing k-map how it is possible to get cell no.....

as mark in box in given image 

Comments

F = A'B + AB'C' +AB

F = A'B(C+C') + AB'C' + AB(C+C')

F = A'BC + A'BC' + AB'C' + ABC + ABC'

$F = \sum ( 2,3,4,6,7)$

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got it thanks bro ...