Answer:
[tex]r=2[/tex]
Step-by-step explanation:
[tex]7r - 1 = 2r + 9[/tex]
Add 1 to both sides:
[tex]7r-1+1=2r+9+1[/tex]
[tex]7r=2r+10[/tex]
Subtract 2r from both sides:
[tex]7r-2r=2r+10-2r[/tex]
[tex]5r=10[/tex]
Divide both sides by 5:
[tex]\frac{5r}{5}=\frac{10}{5}[/tex]
[tex]r=2[/tex]
