Answer:
Hi there!
Your answer is:
66 sandwiches
Step-by-step explanation:
2.2sandwhiches per 1 min
× 30
66 sandwiches per 30 minutes!
Hopefully this helps
In the left hand side, you're multiplying 7.8 by 
In the right hand side, you're multiplying again 7.8 by a mysterious number.
So, the unknown number must be 
Every number remains unchanged when multiplied by 1, so the answer is 3.6