Answer
NOT a solution
Work Step by Step
Substituting the ordered coordinates of $(
1,2
)$ in the given equation, $
c=d+1
,$ results to
\begin{array}{l}\require{cancel}
c=d+1
\\\\
1=2+1
\\\\
1=3
\text{ (FALSE)}
.\end{array}
Since the substitution above resulted in a FALSE statement, then the given point is $\text{
NOT a solution
}$ to the given equation.