1) (3a-3c)+(xa-xc)=3(a-c)+x(a-c)=(a-c)(3+x)

2)(4a+4b)+(by+ay)=4(a+b)+y(a+b)= (a+b)(4+y)

3) (6x+42)+(7y+xy)=6(x+7)+y(7+x)=(x+7)(6+y)

5) (px+py)-(5x+5y)=p(x+y)-5(x+y)=(x+y)(p-5)

6) (ab-ac)-(4b-4c)=a(b-c)-4(b-c)=(b-c)(a-4)