Double a number increased by ten equals twelve express the solution in 3 different ways

Can someone answer it, and plot it, for 20 points and brainliest answer? p.s. they're the same ! : )

The perimeter of a rectangle is 42 inches. if the width of the rectangle is 6 inches, what is the length

Apyramid fits exactly inside a cube. the cube and the pyramid share the same square base, and they are both exactly the same height. the volume of the cube is 66 cubic inches. what is the volume of the pyramid? explain your answer. answer asap