Question 934137
A sum of two numbers is 42.
x+y=42
If one of the numbers is tripled the sum would become 28.
x+3y=28

  x+3y=28
 -x-y=-42
   2y=-14
    y=-7

Substitute y with -7
x+3(-7)=28
  x+-21=28
      x=49
   x+-7=42
      x=49

The numbers are 49 and -7.