Answer:
Therefore the rate of growth of the tree is 33 cm/ yr.
Step-by-step explanation:
Given that,
The height of the tree is
H= 210 +33t
Here H represent the height of tree in cm and t is time in year.
The rate of growth is the first order derivative of the H with respect to time.
i.e The rate of growth 
∴H= 210 +33t
Differentiating with respect to t


Therefore the rate of growth of the tree is 33 cm/ yr.
The blank is 25.
Tip: There is already 25, so there is only 50. But they want half so, half of 50 is 25.
I hope you understand.
Since the water bill costs $35, to split it into 2 equal payments, you would simply just half $35 which is $17.50.
I believe it's the first option. Hope this helps.