Ok, so in order to get tax on something you multiply the amount by the amount of tax in decimal form and then add back the original amount. So for this, you'd start with 8.64*0.07, which equals 0.6048. This rounds to 0.60. 8.64+0.60=9.24
The answer is 30 days until it appears on a Friday again. In order to see the full moon again, we have to go through the entire cycle. So, it will be about 30 days before we would have seen another one.
