21-4r=9

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Solution for 21-4r=9 equation: 


Simplifying
21 + -4r = 9

Solving
21 + -4r = 9

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '-21' to each side of the equation.
21 + -21 + -4r = 9 + -21

Combine like terms: 21 + -21 = 0
0 + -4r = 9 + -21
-4r = 9 + -21

Combine like terms: 9 + -21 = -12
-4r = -12

Divide each side by '-4'.
r = 3

Simplifying
r = 3

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