r = 23
To find this, first combine distribute the numbers, then combine like terms:
4x - 12 - r + 2x = 15x - 35 - 9x
6x - 12 - r = 6 x - 35
Here, the 6x's cancel out so you're left with constants.
-12 - r = - 35
-r = -23
And since -r still is negative, you'll have to divide by - to cancel it out on both sides, leaving you with positive 23 as r.
Hope this helps!
