The numbers x, y and z are successive terms of the arithmetic sequence with a common difference of d=4. What is the sum of these numbers, if the numbers x, y and z+8 are successive terms of the geometric sequence?

An arithmetic progression (also known as arithmetic sequence) is series of consecutive numbers in which every term in the entire series is determined by adding a common difference to the previous term. In other words, if x and y are two successive numbers in an arithmetic term, y can be determined by adding the common difference to x. Similarly, the term that comes after y is determined by adding the same common difference to y.

As stated in the question, the numbers x, y and z are successive terms of an arithmetic progression, and the common difference is given as 4. This simply means;

y = x + 4

z = y + 4

z = (x + 4) + 4

z = x + 8

The terms x, y and z can now be re-written as follows,

x, x + 4, and x + 8

The sum of these numbers therefore is derived as,

Sum = x + x + 4 + x + 8

Sum = 3x + 12