Răspuns :
a+b+c=53
a+b=33
b+c=38
33+c=53
c=53-33
c=20
b+20=38
b=38-20
b=18
a+18=33
a=33-18
a=15
Vf:15+18+20=53
a+b=33
b+c=38
33+c=53
c=53-33
c=20
b+20=38
b=38-20
b=18
a+18=33
a=33-18
a=15
Vf:15+18+20=53