The lifespans of certain batteries are normally distributed. It is found that 15% of battery/less than 30 hours and 10% of batteries last more than 50 hours. Find the mean and standard deviation of the lifespan of the batteries

a net is a diagram that shows a “flattened” view of a solid. in a net, each face and base is shown with all of its dimensions. a net can also serve as a pattern to build a three-dimensional solid.

a pyramid is a three-dimensional object with a base that is a polygon and triangular faces that meet at one vertex.

" the net of a triangular pyramid consists of four triangles. the base here we are given of the pyramid is a equilateral   triangle, and the lateral faces are also triangles "

yes the total will be same because in both of them the expression.is rearranged but their sign remains the same hence it hss just been shuffled