Answer
After replacing the variable name with the given number and evaluating,
if the number is to be a solution,
the resulting equation must be valid (true).
Work Step by Step
The equation features two expressions separated by an equality sign, with one or both expressions containing a variable name (such as x, y, a,b,c...).
Replacing the variable name with the given number and evaluating both expressions,
we arrive at a statement claiming that the number on the left equals the number on the right.
If this is true, the given number is a solution of the equation.
If false, then it is not.
Examples:
the number 2 is a solution of
$2x+3=x+5$
because, after replacing x with 2,
the LHS equals $2(2)+3=7$,
the RHS equals $2+5=7,$
and the statement $7=7$ is true.
The number 2 is not a solution of
$2x+3=x+4$
because, after replacing x with 2,
the LHS equals $2(2)+3=7$,
the RHS equals $2+4=6$,
and the statement $7=6$ is false.
