21=7r-2r

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Solution for 21=7r-2r equation:


Simplifying
21 = 7r + -2r

Combine like terms: 7r + -2r = 5r
21 = 5r

Solving
21 = 5r

Solving for variable 'r'.

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

Add '-5r' to each side of the equation.
21 + -5r = 5r + -5r

Combine like terms: 5r + -5r = 0
21 + -5r = 0

Add '-21' to each side of the equation.
21 + -21 + -5r = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -5r = 0 + -21
-5r = 0 + -21

Combine like terms: 0 + -21 = -21
-5r = -21

Divide each side by '-5'.
r = 4.2

Simplifying
r = 4.2

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