Acertain species of tree grows an average of 0.5 cm per week. write an equation for the sequence that represents the weekly height of this tree in centimeters if the measurements begin when the tree is 200 centimeters tall.

For this we will use equation:

H = starting height + rate_of_growth*periods
We can mark H with index w to represent how many weeks have passed.
Because all of this we can write:

Hw = 200 + 0.5*w

To calculate height after some number of weeks all you need to do is to exchange w with number of weeks.