Answer:
6
Explanation:
I think your question is missed of key information, allow me to add in and hope it will fit the original one. 
Please have a look at the attached photo. 
My answer: 
We need to find the total surface area of the building a skateboard ramp without its bottom. 
- The Area of the slope: 10.5*25 = 262.5 
   
- The Area of the two triangles: 2 (
  ) = 168 ) = 168
   
- The Area of the back: 10.5*7 = 73.5 
   
So the total surface area is: 262.5 + 168 +73.5 = 504 

Hence, the number quarts of paint will mario needs to buy is: 
504/85 ≈ 6 
Hope it will find you well