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x = 18

Step-by-step explanation:

Solve for x:

15 (x - 20) - 21 = 6 - 3 (x + 1)

Hint: | Distribute 15 over x - 20.

15 (x - 20) = 15 x - 300:

15 x - 300 - 21 = 6 - 3 (x + 1)

Hint: | Group like terms in 15 x - 300 - 21.

Grouping like terms, 15 x - 300 - 21 = 15 x + (-300 - 21):

15 x + (-300 - 21) = 6 - 3 (x + 1)

Hint: | Evaluate -300 - 21.

-300 - 21 = -321:

15 x + -321 = 6 - 3 (x + 1)

Hint: | Distribute -3 over x + 1.

-3 (x + 1) = -3 x - 3:

15 x - 321 = -3 x - 3 + 6

Hint: | Group like terms in -3 x - 3 + 6.

Grouping like terms, -3 x - 3 + 6 = (6 - 3) - 3 x:

15 x - 321 = (6 - 3) - 3 x

Hint: | Evaluate 6 - 3.

6 - 3 = 3:

15 x - 321 = 3 - 3 x

Hint: | Move terms with x to the left hand side.

Add 3 x to both sides:

15 x + 3 x - 321 = (3 x - 3 x) + 3

Hint: | Look for the difference of two identical terms.

3 x - 3 x = 0:

15 x + 3 x - 321 = 3

Hint: | Group like terms in 15 x + 3 x - 321.

Grouping like terms, 15 x + 3 x - 321 = (15 x + 3 x) - 321:

(15 x + 3 x) - 321 = 3

Hint: | Add like terms in 15 x + 3 x.

15 x + 3 x = 18 x:

18 x - 321 = 3

Hint: | Isolate terms with x to the left hand side.

Add 321 to both sides:

18 x + (321 - 321) = 321 + 3

Hint: | Look for the difference of two identical terms.

321 - 321 = 0:

18 x = 3 + 321

Hint: | Evaluate 3 + 321.

3 + 321 = 324:

18 x = 324

Hint: | Divide both sides by a constant to simplify the equation.

Divide both sides of 18 x = 324 by 18:

(18 x)/18 = 324/18

Hint: | Any nonzero number divided by itself is one.

18/18 = 1:

x = 324/18

Hint: | Reduce 324/18 to lowest terms. Start by finding the GCD of 324 and 18.

The gcd of 324 and 18 is 18, so 324/18 = (18×18)/(18×1) = 18/18×18 = 18:

x = 18