Răspunsuri

2014-11-16T11:57:16+02:00
Scadem primele 2 ecuatii
- a + c = 20
a + c = 100, le adunam
 /   2c = 120
 c = 120 : 2
c = 60
a + 60 = 100
a = 100 - 60
a = 40
40 + b = 90
b = 90 - 40
b = 50