12% of 72 is what number

Which is an equation for the nth terms of the sequence 12,15,18,21

Consider the integral: 4 0 16 − y2 − 16 − y2 4 1 x2 + y2 dz dx dy . (a) describe w. use the standard view of the x, y, and z axes. front half of a cone with a rounded top. full cone with a flat top. right half of a cone with a flat top. front half of a cone with a flat top. right half of a cone with a rounded top.

What is the value of x in the diagram below?