hi AlbertMThomas

If water is poured into the container at a rate of 2t + 2 m³ per minute where t is the time.

Think about what that rate represents:

It's in cubic metres per minute so that's

At the start t = 0 and V = 0. At the end V = 15 at (say) t = T

So integrate to get V in terms of t; put V = 15 (the constant of integration will come from t = V = 0) and solve for T

Bob