### Instruction: John is 31 years younger than his dad. The sum of their ages is 53 years. How many years old is John's dad?### Response: To solve this problem, I need to find a way to relate John's age and his dad's age using algebra.
Let me call John's age x and his dad's age y.
Then I have two equations: x = y - 31 and x + y = 53.
I can substitute x = y - 31 into the second equation and get: y - 31 + y = 53.
This simplifies to 2y = 84, so y = 42.
This means John's dad is 42 years old.