algebra
posted by rachel on .
you are driving at a speed of 55 miles per hour to your sister's house. at 1pm, you are 150 miles from her house. write an equation that models the distance from you sister's house in terms of the number of hours since 1pm.

We need a variable for the time. Let's call that t. And we can call the distance d.
At t = 0 (1pm) you are 150 miles away, and as t increases, the distance decreases, so we need to subtract some multiple of t from 150 as we go.
We need something that starts with
d =
since the distance is what we want to know, and the right hand side will be like
150  something * t
Of course, technically, we'd need to limit the domain of t; otherwise, after 10 hours, we'll be negative miles away. 
It's b boib boib bo ibboi boib