If she put the marbles in 4 bags with m marbles in each bag and she had 3 marbles left over that didn't fit in the bags, then the number of marbles that she has is 4m - 3
Number of bags that she has = 4 bags
The number of marbles in each bag = m marbles
Number of marbles left over = 3 marbles
Then the expression that represents the number of marbles that she has is
4m - 3
Where m is the number of marbles in each bag
Hence, if she put the marbles in 4 bags with m marbles in each bag and she had 3 marbles left over that didn't fit in the bags, then the number of marbles that she has is 4m - 3