21=r+4

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Solution for 21=r+4 equation:


Simplifying
21 = r + 4

Reorder the terms:
21 = 4 + r

Solving
21 = 4 + r

Solving for variable 'r'.

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

Add '-1r' to each side of the equation.
21 + -1r = 4 + r + -1r

Combine like terms: r + -1r = 0
21 + -1r = 4 + 0
21 + -1r = 4

Add '-21' to each side of the equation.
21 + -21 + -1r = 4 + -21

Combine like terms: 21 + -21 = 0
0 + -1r = 4 + -21
-1r = 4 + -21

Combine like terms: 4 + -21 = -17
-1r = -17

Divide each side by '-1'.
r = 17

Simplifying
r = 17

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