Solve the below given problem:
 
A toy car moves with a speed of \(15\ m/s\). Due to friction, its speed decreases to \(6\ m/s\) in \(5\ seconds\).

Find the acceleration of the toy car.
 
The acceleration of the toy car \(=\) \( ms^{-2}\)
 
[Note: Enter the answer with one decimal value]