Answer:
R = 8.3144598 J. mol-1. K-1.
Step-by-step explanation:
r=9
7r-5=6r+4
[tex]7r-5=6r+4\\-6r -6r\\1r-5=4\\ +5 +5\\\frac{1r}{1} = \frac{9}{1} \\r=9[/tex]
hope this helps