21-3a=-7(a-7)

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Solution for 21-3a=-7(a-7) equation:


Simplifying
21 + -3a = -7(a + -7)

Reorder the terms:
21 + -3a = -7(-7 + a)
21 + -3a = (-7 * -7 + a * -7)
21 + -3a = (49 + -7a)

Solving
21 + -3a = 49 + -7a

Solving for variable 'a'.

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

Add '7a' to each side of the equation.
21 + -3a + 7a = 49 + -7a + 7a

Combine like terms: -3a + 7a = 4a
21 + 4a = 49 + -7a + 7a

Combine like terms: -7a + 7a = 0
21 + 4a = 49 + 0
21 + 4a = 49

Add '-21' to each side of the equation.
21 + -21 + 4a = 49 + -21

Combine like terms: 21 + -21 = 0
0 + 4a = 49 + -21
4a = 49 + -21

Combine like terms: 49 + -21 = 28
4a = 28

Divide each side by '4'.
a = 7

Simplifying
a = 7

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