Question

How to solve the system of equations that answers as all real numbers?

Answer 1

You can solve a system using substitution, elimination, or graphing method.

If you solve using substitution or elimination, the variable will cancel out on both sides and you will be left with a number equal to a number.  If "number = number" is a TRUE statement, then the solution is ALL Real Numbers.  If it is a FALSE statement, then you will have NO solutions.

If you solve using the graphing method and the lines are exactly the same, then the solution is Infinite solutions (aka ALL Real Numbers).  If the lines are parallel, then you will have NO solution.