Răspuns :
(a+b+c+d+e):5=1/10
(a+b+c+d+e)=1/10x5
(a+b+c+d+e)=1/2
(a+b+c+d):4=1/20 =>a+b+c+d=1/20x4 simplificam cu 4
a+b+c+d=1/5
1/5+e=1/2
e=1/2-1/5
e=(5-2)/10
e=3/10
verificare
(1/5+3/10):5=
5/10x1/5=1/10
(a+b+c+d+e)=1/10x5
(a+b+c+d+e)=1/2
(a+b+c+d):4=1/20 =>a+b+c+d=1/20x4 simplificam cu 4
a+b+c+d=1/5
1/5+e=1/2
e=1/2-1/5
e=(5-2)/10
e=3/10
verificare
(1/5+3/10):5=
5/10x1/5=1/10