a+b+c+d+e+f+g+h=432---(1)
a+b+c+d+e=230--------------(2)
e+f+g+h=272-------------------(3)
sub (2) into (1)
230+f+g+h=432
f+g+h=202-----------------------(4)
sub (4) into (3)
e+f+g+h=272
e+202=272
e=70
所以第五個數是70OR
a+b+c+d+e+f+g+h=432---(1)
a+b+c+d+e=230--------------(2)
e+f+g+h=272-------------------(3)