Sales tax = 6% or 6/100.
assuming tax is added onto the item:
total cost function f(x) = price + tax
however, assuming the cost price = sales price - tax, then:
f(x) = sales price - tax
This is not really a business or accounting forum, its a maths forum, so you need to be clearer about business or accounting terms such as total cost, selling price, selling cost.
I’m pretty sure there are infinite solutions as the system of equations are equivalent to each other.
At a race, there are 3 rows with 15 people in each row. How many total people are there?
Numerical expression- 15 times 3
(Idk if this helped very much but it's worth a shot)