Ellen has 15 marbles, and Carlos has 12 marbles. They put their marbles together. The letter $m$ stands for the total number of marbles. We need to find the equation that can be used to find $m$.

1. Problem Description

Ellen has 15 marbles, and Carlos has 12 marbles. They put their marbles together. The letter $m$ stands for the total number of marbles. We need to find the equation that can be used to find $m$.

2. Solution Steps

Since Ellen and Carlos are putting their marbles together, we need to add the number of marbles each person has to find the total number of marbles. Ellen has 15 marbles, and Carlos has 12 marbles. Therefore, we need to add 15 and 12 to find $m$.

The correct equation is:

$15 + 12 = m$

3. Final Answer

$15 + 12 = m$