Now find Y
I'd get rid of that book . . . it's juvenile.
And, I'm afraid, so are you . . .
The book had the following answer for C.
What a stupid way to publish an answer!
Did you simplify it?
It's obvious that it never occured to them !
I'll start over . . .
We have: .
Add the equations: .
Substitute into : . . and they stopped here?!
. . Therefore: .