a sheet of 8 x 4 ply how many sheets to cover 13ft 6 x 13 ft

clearly you will have to cut some of the 4x8's

If we place the long side of the 4x8 along the long side of the floor, we will need 3 sheets, with some cut off.
We will then have the 4 ft part along the 13 ft part of the floor, needing 4 sheets with lots of waste.
This "textbook" question probably expects an answer of 12 sheets.

In reality, some other factors have to be considered.
According to building codes, the pieces of plywood have to be staggered so that any four sheets do not meet at 1 intersection point. They have to be laid similar to bricks. That would affect the pieces that are left over.
Also, according to different building codes , the number of smaller pieces along a side must have certain minimum lengths.

Not a straightforward question. You could take a grid marked in feet, then cut out pieces of 4x8 from another sheet of paper and try to fit them.

The definitely wrong approach is to take
13.5 x 13= 175.5 square ft, and then divide that by 32 square ft to get 5.48 or 6 sheets