Please answer the question in the pic

Which equation can be used to measure the density of water in a spherical water tank? let w represent the number of water particles within the region.

5cakes cost 3.50 how much do 7 cakes cost

If you were constructing a triangular frame, and you had wood in the length of 4 inches, 4 inches, and 7 inches, would it make a triangle? would you be able to create a frame from these pieces of wood?