Answer: 50
Explanation:
10+15+6+4+6+11= 50
Edit=
We can see that the length of one side is 10, and the width of one is 15. For the other side of the width, we can subtract 4 from 15 to get 11. For the other length, we can subtract 6 from 10 to get four. We also have to add in the 6 and 4 because they are parts of the border. (10+15+11+4+6+4)