#### Answer

a contradiction;
no solution

#### Work Step by Step

Using the properties of equality, the given equation, $
13x-(x+7)=12x-13
,$ is equivalent to
\begin{array}{l}\require{cancel}
13x-x-7=12x-13
\\\\
13x-x-12x=-13+7
\\\\
0=-6 \text{ (FALSE)}
.\end{array}
Since the solution above ended with a FALSE statement, then the given equation is $\text{
a contradiction
.}$ Hence, there is $\text{
no solution
}.$