A sandwich costs $0.75 more than a container of milk. A customer buys 4 sandwiches and 4 containers of milk. The customer pays $7.00. What is the cost of a sandwich?

Let x be the cost of a sandwich

7 = 4x + 4 (x-0.75)
7 = 4x + 4x - 3
10 = 8x
8x = 10
x = 10/8
x = 1.25
A sandwich is $1.25