Important occasions are often celebrated in a what way

Special? big? There a quite a few words that could fit here.

To find the answer first we will multiply to see how much the books cost. Then we will subtract 50 by the amount of money she has to pay. Then we will check our work to makes sure we are %100 right. Lets do it:-

Lets multiply:-
10 × 2 = 20
So, 10 books cost 20m.

 Lets subtract:-

50 - 20 = 30
So she gets 30m in chage.

CHECK OUR WORK:-

30 + 20 = 50
We were RIGHT!!!

So, Coley would receive 30m (B) 30m) in change is she pays with a 50 dollar bill. 

Hope I helped ya!!