Let the cost of one sandwich be x. You order three sandwiches, so the cost for all three sandwiches is 3x.
The pre-tax total for three sandwiches and a drink is:
3x + 1.75
The tax on this amount is 8%, so the tax is:
0.08 × (3x + 1.75)
The total amount with tax, before adding the tip, is:
3x + 1.75 + 0.08 × (3x + 1.75) = 1.08 × (3x + 1.75)
After adding the $5 tip, the total is $20.66:
(3x + 1.75) × 1.08 + 5 = 20.66
Now, we just solve for x:
3.24x + 1.89 + 5 = 20.66 (distribute the 1.08)
3.24x + 6.89 = 20.66 (add like terms)
3.24x = 13.77 (subtract 6.89 from both sides)
x = $4.25 (divide both sides by 3.24)
The cost of one sandwich is $4.25.
Hope this was helpful.
