Answer :
[tex]6r+7=13+7r \\ -6r\ \ \ \ \ -6r \\ 7=13+r \\ -13\ \ -13 \\ -6=r[/tex]
You need to get the r by itself on one side, with the constants (numbers without the r) on the other side.
[tex]6r+7=13+7r\\6r-7r+7=13+7r-7r\\-r+7=13\\-r+7-7=13-7\\-r=6\\-r/-1=6/-1\\r=-6[/tex]
[tex]6r+7=13+7r\\6r-7r+7=13+7r-7r\\-r+7=13\\-r+7-7=13-7\\-r=6\\-r/-1=6/-1\\r=-6[/tex]
