What should i do ? where it’s say ‘ start here ‘?

Yes, you are going to start the maze in the box that says "Start Here". For the first box we are trying to find the length of AB. Notice that AB + BC = AC. If we substitute our known values for AB and BC, we find that we obtain the equation:

By simplifying our equation and isolating , we can find our

The length of AB is 4.

i got 10.28 but that rounds up to 10.3