To find out how many grilled cheese sandwiches Mega Melt's food truck will make today, we first need to determine their rate of making sandwiches.
Yesterday, they made 56 grilled cheese sandwiches in 2 hours. We can calculate the rate of sandwiches made per hour by dividing the total number of sandwiches by the number of hours:
\[ \text{Rate} = \frac{\text{Total sandwiches}}{\text{Total hours}} = \frac{56 \text{ sandwiches}}{2 \text{ hours}} = 28 \text{ sandwiches per hour} \]
Now, if the food truck will be open for 3 hours today, we can calculate the total number of sandwiches they will make by multiplying the rate by the number of hours:
\[ \text{Total sandwiches today} = \text{Rate} \times \text{Hours} = 28 \text{ sandwiches per hour} \times 3 \text{ hours} = 84 \text{ sandwiches} \]
Thus, Mega Melt's food truck will make 84 grilled cheese sandwiches today.