Add the veggieburger, soup, and cola prices together.
3.25 + 2.25 + 1.5 = x
Multiply by 0.04 to get the sales tax, then add the food cost to the tax.
0.04x + x = y
Multiply result by 0.15 to get the tip, then add the tip to the food cast and tax total.
0.15y + y = ?
