Concept:Factorise by grouping: put the four terms in two pairs, take the common factor out of each pair, then take out the bracket that both pairs share.Solution:Group the terms that contain y and the terms that do not: (5ay−by)+(15a−3b)First pair: y is common, so 5ay−by=y(5a−b)Second pair: 3 is common, so 15a−3b=3(5a−b)Now both parts contain the bracket (5a−b): y(5a−b)+3(5a−b)Take (5a−b) out: (y+3)(5a−b)Check by expanding: (y+3)(5a−b)=5ay−by+15a−3b ✓Answer:Option A ((y+3)(5a−b))