1.)If a|bc then a|c

let a = 2 and b = 5 and c = 20

so (5)(20) / 2 = 50

then 20/2 = 10

what if we let a = 3 b= 7 c = 4

(7)(4)/3 = 28/3 = has a remainder... will this be considered true?

2.)if a|c and b|c then ab|c

let a = 2 and b = 5 and c = 20

so 20/2 = 10 and 20/5 = 4 then 20/(2)(5) = 20/10 = 2

what if we let a = 3 b= 7 c = 4

4/3 = 2 and 4/7 = has remainder... will this be considered true?

How can we prove this ... please help.... thanks