Set up a proportion like this

=
So your proportion would be:

We put x for offices because they are asking for the number o offices a crew can paint in 12 hours, and also we don't know the number of offices they can paint in 12 hours
so we cross multiply and we get
6x=60, we got 60 by multiplying 12 and 5
Now we divide both sides by 6 and we get
x=10
S the crew can paint 10 offices in 12 hours.
y² = 8y - 15 (alternate angles are equal)
y² - 8y + 15 = 0
(y - 5)(y - 3) = 0
y = 5 or 3
x + 8y - 15 = 180 (angles in a straight line add up to 180)
when y = 5
x + 40 - 15 = 180
x = 155°
when y = 3
x + 24 - 15 = 180
x = 171°
The answer is 6/6 so does that help you today and it can also be one whole
You replace x with (a+1)
Then f(a+1) = (a+1)^2+1
= a^2+2a+1+1
= a^2+2a+2