Răspuns :
a+b+c+r==91
b+c+r=28
a=91-28=
a=63
a+r=74
r=74-63
r=11
b+c=28-11
b+c=17
63=bxc=11
bxc=63-11=52
52=4x13
b=13
c=4
b+c+r=28
a=91-28=
a=63
a+r=74
r=74-63
r=11
b+c=28-11
b+c=17
63=bxc=11
bxc=63-11=52
52=4x13
b=13
c=4