Final answer:
A multiplication sentence representing Matt making 3 equal groups of marbles is '3 × x', where x is the number of marbles in each group. The product gives the total number of marbles.
Step-by-step explanation:
When Matt makes 3 equal groups of marbles, the total number of marbles can be represented using a multiplication sentence.
To construct the multiplication sentence, you need to know the number of marbles in each group. Let's assume there are x marbles in each group. Since there are 3 equal groups, the multiplication sentence would be 3 × x. Here, 3 represents the number of groups, and x represents the number of marbles in each group.
The result of the multiplication will give you the total number of marbles Matt has. Keep in mind that without knowing the exact number of marbles in each group, we can't give the specific total number of marbles, but this sentence structure is how you would represent the situation mathematically.