It looks like you're trying to solve
3x₁ + 7x₂ + s₁ = 49
x₁ +4x₂ +s₂ = 31
Fill in the given values for x₁ and s₁ and your system reduces to
7x₂ = 49
4x₂ +s₂ = 31
The first of these equations tells you x₂ = 49/7 = 7, so the second equation becomes
28 +s₂ = 31
and it is immediately obvious that s₂ = 3
Your solution is (x₁, x₂, s₁, s₂) = (0, 7, 0, 3).
