Answer:
r = -6
Step-by-step explanation:
basically send the letters on one side (preferably the left) of the = sign... and the numbers on the other side. Remember when you pelting things across the equal sign, you have to switch the signs... meaning positive (+) will become negative (-) or vice versa...
6r + 7 = 13 + 7r
6r - 7r = 13 - 7
-1r = 6
r = -6
