18-a=21

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Solution for 18-a=21 equation:


Simplifying
18 + -1a = 21

Solving
18 + -1a = 21

Solving for variable 'a'.

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

Add '-18' to each side of the equation.
18 + -18 + -1a = 21 + -18

Combine like terms: 18 + -18 = 0
0 + -1a = 21 + -18
-1a = 21 + -18

Combine like terms: 21 + -18 = 3
-1a = 3

Divide each side by '-1'.
a = -3

Simplifying
a = -3

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