00:01
Okay, in this problem, we're just going to call bookstore a, a, bookstore b, b, and bookstore c, c.
00:06
So it's super easy to keep track of.
00:08
So, we shipped a total of 800 t -shirts.
00:12
So, both t -shirts at a plus t -shirts at b plus t -shirts at c must be 800.
00:22
And we know we have twice as many t -shirts at b than a.
00:27
So we can say b equals 2 times a.
00:36
And the number at c was 40 less than the other two.
00:44
So c is the other two, a plus b, minus 40.
00:54
So now we have our two equations.
00:57
Let's go ahead and substitute a down here.
01:03
So i'm going to say c equals a plus 2a minus 40.
01:16
So we can say c equals, let's just remember those are original three.
01:22
C equals 3a minus 40.
01:25
So c equals 3a minus 40 and b equals 2a.
01:29
So now we can plug in.
01:31
We're going to leave a the same, but b we're going to call 2a and c we're going to call 3a plus 40 or 3a minus 40...