What number must be added to each of 4, 7, 12 so that the resulting numbers form a geometric sequence?

Answer 1

how about solving:

(7+x)/(4+x) = (12+x)/(7+x)

Answer 2

You want a constant ratio, so

(7+x)/(4+x) = (12+x)/(7+x)
x = ?

Answer 3

1/2