Hey! I don't know this, can you explain to me? Link: https://justpaste.it/2e96a?

Easy.  Let's use the variable b for the number of marbles in a bag.

You bought 3 bags, so you have 3b marbles.
Your friend bought one bag but he also has 24 marbles, so he has b + 24 marbles.

Now you both have the same amount  So, 3b = b + 24.  That's our equation.  Now we solve for b.

3b = b + 24

Let's subtract b from both sides.

2b = 24

So now it's simple.  Divide both sides by 2.

b = 12

And there ya go....Show more