Answer:
x = -6.5 meters
Explanation:
The position of a ball as a function of time t is given by :
..................(1)
Where t is time in seconds
We need to find the position of the ball at 1.9 s. It can be simply calculated putting t = 1.9 s in equation (1) as :

x = -6.5 meters
So, the position of the ball at 1.9 seconds is -6.5 meters. Hence, this is the required solution.
The dimension of a/b where x is the distance and t is the time is T
Given the expression
x = at + bt²
where
x is the distance
t is the time
Based on the homogeneity principle, the expression on the left-hand side must be equal to that on the right. Hence;
x = at

Since x is the distance and distance is measured in metres, the dimension equivalent will be the length 'L'
Since t is the time and time is measured in seconds, the dimension equivalent will be the seconds 'T'

Similarly;
x = bt²

Next is to get a/b;

Hence the dimension of a/b is T
I hope that helps you!!!!!!
As you said p=w/t.
but, w=f×s
=500×5=2500j
t=10s
p=w/t
=2500/10=250 watts