Hello, LN!
If you don't show us your work, we can't tell you what you're doing wrong ...
duh!
The right answer is
r=1 . . . but, of course, you know that, right?
I'll do the whole problem for you
and you'll answer, "Oh, I forgot the minus.
or worse . . . "I was looking at the wrong answer ...hahaha!"
Okay, I'll
do it for you . . . just this once.
We are given: \(\displaystyle \L\;7[2\,-\,(3\,+\,4r)]\,-\,2\;=\;-9\,+\,2(1\,-\,15r)\)
The left side is:
7[2−3−4r]−2=7[−1−4r]−2=−7−28r−2=−28r−9
The right side is:
−9+2−30r=−7−30r
The equation becomes: \(\displaystyle \L\;-28r\,-\,9\;=\;-7\,-\,30r\)
Can you finish it now?