PLEASE HELP AND SHOW WORK

7.5

Step-by-step explanation:

If we look at the 4 by 4 square around the triangle we can just do the area of the square minus the area of the 3 little triangles which is:

4 * 4 - 4 * 1 / 2 - 3 * 3 / 2 - 4 * 1 / 2

= 16 - 2 - 4.5 - 2

= 16 - 8.5

= 7.5

answer: all of the odd numbers were opened

the first person was the one that was opening all of the lockers. since one is odd, this causes all of the odd number lockers to be opened in the end.