Explicație pas cu pas:
a+b+c+d=704
a+7=b-7=c*7=d/7=k
a+7=k=>a=k-7
b-7=k=>b=k+7
c*7=k=>c=k/7
d/7=k=>d=7k
k-7+k+7+k/7+7k=704
9k+k/7=704 /*7
63k +k= 4928
64k=4928
k=77
a=70
b=84
c=11
d=539
