Question

How to check the solution of linear equation

Answer 1

You can check by substituting your solution values into the given equation nd verify that it is satisfied.
If you are talking about an equation in 1 variable suppose the equation is 3x + 15 = 21
if you got the answer x = 2, on substituting x = 2 the equation left hand side is 3(2) +15 = 21
so it is verified.
Similar approach with equation in 2 variables
x + y = 9
2x+3y = 23
If your solution is x = 4 and y = 5 substitute in both equations and verify them
4+5 = 9 so correct
2(4) +3(5) = 23 so also verified