Answer:
[tex]\boxed{\sf r=10}[/tex]
Step-by-step explanation:
[tex]\sf 4(2r+5)=10r[/tex]
Expand: Use the Distributive Property to multiply 4 by 2r+5:
[tex]\longmapsto\sf 8r+20=10r[/tex]
Subtract 20 from both sides:
[tex]\longmapsto\sf 8r+20-20=10r-20[/tex]
[tex]\longmapsto\sf 8r=10r-20[/tex]
Subtract 10r from both sides:
[tex]\longmapsto\sf 8r-10r=10r-20-10r[/tex]
[tex]\longmapsto\sf -2r=-20[/tex]
Divide both sides by -2:
[tex]\longmapsto\sf \cfrac{-2r}{-2}=\cfrac{-20}{-2}[/tex]
[tex]\longmapsto\sf r=10[/tex]
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