(a) Use the following formula:

where:
P2 = 525
P1 = 425
t2 = 2020
t1 = 2018
Replace the previous values into the expression for d:

Hence, the growth rate is 50 homes per year.
(b) Due to you can take t = 0 for the counting of homes from 2018, you can write the following linear equation:

(c) Replace t = 2026 - 2018 = 8, into the expression for P(t):

There will be 825 homes in 2026.
(d) Replace P(t) = 675 and solve for t:

Then, by considering that 2018 is for t = 0, you have for t = 4:
2018 + 4 = 2022
During the year 2022 the number of homes will exceed 675 homes.