Question

If x-y =20 & x+y=40, then x=? Y=?

Answer 1

             x-y=20
             x+y=40
            ________
            2x=60

             x=30

     ==>>  x+y=40
              30+y=40
              
                y=10

Answer 2

x-y=20
Therefore x=20+y
x+y=40
Substituting value of x from the first equation
20+y+y=40
2y=40-20=20
y=10
Therefore,
x=20+10=30

Answers:
x=30
y=10