goal seeker or solver for forecasting vs. actuals

Do you really need “Goal Seek” or Solver?

You problem is (15 + X*11)/12 = 13 and reshuffling that by multiplying both sides with 12 and keeping X on the left side of the equation you get X =(13*12 -15)/11 i.e.

for the rest of year (11 months) the growth must be 12,818 % /month in order to get 13 % as the average.

Alf

Basic math over excel!!! I like it....