Question

3. Dacă x+y=12 şi x-y-10 atunci x=.......si y=.......​

Answer 1

x+y=12

x-y=10 => x=10+y si se introduce in prima ecuatie

x+y=(10+y)+y=12 => 2y=2 =>y=1

=> x=10+y=10+1 =>x=11

Solutie: x=11 si y=1

Answer 2

x+y=12 inseamna ca x=12-y.
Il inlocuiesti pe x in cealalta ecuatie si obtii:
12-y-y=10
12-2y=10
2y=12-10
2y=2
y=1
Deci x=12-1
x=11