2 bags
7 apples
A) Instead of a lets say:
a = 1, 2 , 3
If a =1 then, (you already know there are 2 bags) you have 1 apple in each bag, making total of 2 apples
If a =2 then you are having 2 apples in each bag making total of 4 apples
If a =3, 3 apples in each bag, making total of 6 apples
Conclusion:
2 * 1 = 2
2 * 2 = 4
2 * 3 = 6
See the difference & pattern here
Now lets do with a
2 * a = 2a
B) If a = 6
then, 2*6 = 12
lets continue from a =3
2*4=8
2*5=10
2*6=12
See the pattern again
Tip: Drawing making problem understand better.