Hi the one written in light green is for the second question. For the second question solution, there are two pythagoras theorem that i used for two triangles. The first pythagoras theorem is used for the triangle highlighted in green, to find the diagonal length of the one side of the cube. The second pythagoras theorem is used for the triangle highlighted in red to find the diameter of the sphere. Hope this helps! Do contact me at 9620 6785 if you require tuition services.