Answer Happy

Please explain how to solve, thank you!
In Problems 11-15, let R be the region bounded by the lines y = 4-x, x= -2, and the x-axis. Each problem will describe the cross sections of a solid. Find the volume of that solid (you do evaluate these problems). 11) The cross sections are squares perpendicular to the x-axis with one edge in R. 12) The cross sections are semicircles perpendicular to the y-axis with the diameter in R. 13) The cross sections are equilateral triangles perpendicular to the x-axis with one edge in R. 14) The cross sections are squares perpendicular to the y-axis with the diagonal in R. 15) The cross sections are circles perpendicular to the x-axis with the diameter in R.