Answer: The expression that can be used to find the cost of x sandwiches is 6.25x.
Explanation:
Given: Cost of 5 sandwiches = $31.25
To find : Cost of x sandwiches.
Cost per sandwich = ( Cost of 5 sandwiches) ÷ 5
= (31.25 )÷ 5
= $ 6.25
Cost of x sandwiches = (Cost per sandwich) × (x)
= 6.25x
Hence, the expression that can be used to find the cost of x sandwiches is 6.25x.