A + B = 40 lei
A - 6 = (B +6) : 3 ==>
==> 3×A - 18 = B + 6
==> 3×A - B = 6+18
==> 3×A - B = 24
A + B = 40
3×A-B = 24
------------------ adunam cele doua relatii
4×A = 64
A = 64 : 4
A = 16 lei are Ana
B = 40 - 16 = 24 lei are Bogdan
Verificam:
16 + 24 = 40
16 - 6 = (24 + 6) : 3
10 = 30 : 3
10 = 10 (adevarat)