设B为X岁,则A=X-4;C=X-2;D=(X-2)+4=X+2;吉姆=X+2-8=X-6.
(X-4)+X+(X-2)+(X+2)+(X-6)=75
5X-10=75
X=17
A=13;B=17;C=15;D=19;吉姆=11