Mariana buys a snack combo for $2.50. if the sales tax rate is 8% , what is the total price for the combo including ,the tax?

Find 8% of the price of the snack combo. Do this by setting up a proportion and cross multiplying to solve for x. This will look like:

=

Basically, you set it up like this because you want to find what value of x will be equal to 8% over 100%. In order to figure out what x is, you will need to cross multiply the two diagonal from each other, and then divide whatever answer you get from the 3rd number. This will be:
2.5*8 = 20
20/100 = 0.20 cents

0.20 cents is your tax. So add that to your price, $2.50, and you will have your total price.

You get: $2.70