vaaaa rpgggggggg!!!!!

Vaaaa Rpgggggggg class=

Răspuns :

a+b = 20 => a = 20-b

3a+5b = 90 => 3(20-b)+5b = 90 => 60-3b+5b = 90 =>

=> 2b = 90-60 => b = 30:2 => b = 15 inecuatii

a = 20-15 = 5 ecuatii

x - ecuatiile si y - inecuatiile

x+y = 20 ⇒ x = 20-y

3x+5y = 90

3(20-y)+5y = 90

60-3y+5y = 90

2y = 90-60

y= 30/2

y= 15 inecuatii

x== 20-15

x= 5 ecuatii