Question 103256
Let x= the first no.
    y= the other no.

(1)x+y=30
(2)x-y=40
From (2),
x=y+40, substituting this to (1),

y+40+y=30
 2y+40=30
    2y=-10
     y=-5

Solving for x,
x-5=30
  x=35
Therefore, the 2 nos. are 35 and -5