PLEASE HELP ME What do we mean when we say like terms? what do we mean when we say combining like terms? how do polynomials demonstrate the closure property under addition and subtraction?

Find solution of the linear equation y = 2/3x + 1/3

For every corresponding pair of cross sections, the area of the cross section of a sphere with radius r is equal to the area of the cross section of a cylinder with radius and height 2r minus the volume of two cones, each with a radius and height of r. a cross section of the sphere is and a cross section of the cylinder minus the cones, taken parallel to the base of cylinder, is the volume of the cylinder with radius r and height 2r is and the volume of each cone with radius r and height r is 1/3 pie r^3. so the volume of the cylinder minus the two cones is therefore, the volume of the cylinder is 4/3pie r^3 by cavalieri's principle. (fill in options are: r/2- r- 2r- an annulus- a circle -1/3pier^3- 2/3pier^3- 4/3pier^3- 5/3pier^3- 2pier^3- 4pier^3)

Triangle abc was translated 2 untits to the right and 3 units down. write the algebraic rule that describes the translation that was applied to triangle abc to create triangle a'b'c'.