How can you determine the total cost of an object of an item including tax if you know the price and the tax rate

I can give you variables to show the tax and price.
price = p
tax=t
c=cost


You have to put the tax back in the initial form, so you divide by 100. You then want to find the percentage of the price of the item by multiplying it. You add it on to the tax because you can't just pay the tax and not pay for the item, you have to pay for both.

Tell me if this helps!!

1. 0.3 •4 is the same as 4 groups of 0.32. 7•0.8 is the same as 7 groups of 0.83. it increases by 0.5 every time, so 0.5x4 it increases by 0.9 every time, so 0.9x5. 0.9•12=10.86. 0.47•5=2.35i can finish the next ones in a separate post