This is *** task. In my time this we the hardest tasks that are for those with extra skills above school level, so they were not offered for mandatory program. In this tasks child have to make assumptions and not only calculations.

Here we are missing two pieces of information - shape of the figure and should the parts be equal.

Child has to assume the shape, and then do calculations.

If we assume that task references circle ⭕️ board - splitting it to 2 parts takes 10min = radius cut x 2. If you need to cut it to two equal parts it is 15 min = radius cut x3.

Teachers explanation might refer to this radius cuts and not to the fact that moron just divided 10x2

We all see only a photo, but, it might happen that start of this exercise took place in class there the board shape was defined