Question

a+b=50. a-b=30. a,b=?

Answer 1

a+b = 50
a - b = 30
      ⇵
  a = (50+30):2 = 40   si   b = (50-30):2 = 10

Answer 2

a+b=50
a-b=30
a=30+b
inlocuim CU a=30+b
avem
a+b=50
30+b+b=50
b+b=50-30
2b=20
b=20:2
b=10

inlocuim CU b=10
a+b=50
a+10=50
a=50-10
a=40

40+10=50