First, you have to find out what's 7% of $80. So what you do is multiply 80 by 0.07, which leaves you with $5.60. Add 5.6 to 80 so you get 85.6. Now you have to find how much the 20% of 80 is. So you multiply 80 by 0.2, leaving you with 16. So you subtract 16 from 85.6, leaving you with 69.6. So the total cost of the skateboard would be $69.60.