Question 1102378
Question not clear.  I can answer what was the national wealth in 1985 if in 2015 it was estimated at 3.125*10^12 (not 10*12, which would be too small).
3.125*10^12=Po(1+.04)^30; 1.04^30=3.243, but round only at end
divide both sides by 3.243
Po(1985)=9.635*10^11
If the question is different, resubmit, but that is how one would work back.