Answer:
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:
Answer: x = 18
. We will simplify that and at the same time bring the 6 over by subtraction to get a polynomial set to equal 0 that we can factor. 
. We will factor that to get (x-3)(x+1) for x values of x = 3 and x = -1. a above is the choice that has the x values we need, -1 and 3.