Let $j$ be John's age and $d$ be his dad's age. We are trying to find the value of $d$. We can create a system of two equations to represent the given information. They are

\begin{align*}
j &= d - 31 \\
j + d &= 53 \\
\end{align*}

We want to find $d$, so we need to eliminate $j$ from the equations above. Substituting the first equation into the second to eliminate $j$, we have $(d-31)+d=53$, or $d=42$. Thus, John's dad is $\boxed{42}$ years old.
John is 31 years younger than his dad. The sum of their ages is 53 years. How many years old is John's dad?
{'answer': '42', 'subject': 'Algebra', 'level': 2, 'unique_id': 'test/algebra/2278.json'}