How does acceleration values differ mathematically from deceleration values?

If a problem says the acceleration is some positive value than solve using that value, a negative acceleration is said to be deceleration. E. g. a car decelerating at 10 m/sec can be said to be accelerating at - 10 m/sec.

If a problem states decelerates at A, then use - A for acceleration in the classic equations which are for acceleration. If a problem says accelerates at a negative value like - A the use - A as the value for acceleration, it can also be said to be decelerating at A.