You decide to give 18 of your card collection to your little brother. how much of your collection do you have left?

The answer is

Step-by-step explanation:

In order to determine the answer, we have to build the expression that represents the remain collection.

According to the statement, we do not know the initial collection, but we can express this amount with a variable:

C=initial collection cards

Then, we know that we have to give 18 card to the little brother, so we have to subtract 18 to the initial collection.

The expression for the remain cards is:

ca = ec

cpctc makes it so that corresponding parts of the triangle you proved to be equal are equal, the other options aren't part of the part of the triangles you proved to be equal.