In order to find the tax of something, you would take the total number and multiply it by the amount of percent the tax is.
46.50 is the total without the tax and 6% tax adds 6 cents to every dollar of the pre-tax sum.
So dinner before the tax would be $45.
Now if you wanted to leave a tip of 20%, you would basically find out $45/5, which is 9.
So the tip would basically be $9.