Question

A.)List the 4 steps outlined in the lesson on solving equations.

Answer 1

1.) Solve for x:
5 x + 7 = 3 x + 21

Subtract 3 x from both sides:
(5 x - 3 x) + 7 = (3 x - 3 x) + 21

5 x - 3 x = 2 x:
2 x + 7 = (3 x - 3 x) + 21

3 x - 3 x = 0:
2 x + 7 = 21

Subtract 7 from both sides:
2 x + (7 - 7) = 21 - 7

7 - 7 = 0:
2 x = 21 - 7

21 - 7 = 14:
2 x = 14

Divide both sides of 2 x = 14 by 2:
(2 x)/2 = 14/2

2/2 = 1:
x = 14/2

The gcd of 14 and 2 is 2, so 14/2 = (2×7)/(2×1) = 2/2×7 = 7:
Answer:  x = 7

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2.)  Solve for x:
3 x - 2 (5 - x) = 3 x - 3 (x - 10)

-2 (5 - x) = 2 x - 10:
2 x - 10 + 3 x = 3 x - 3 (x - 10)

Grouping like terms, 3 x + 2 x - 10 = (3 x + 2 x) - 10:
(3 x + 2 x) - 10 = 3 x - 3 (x - 10)

3 x + 2 x = 5 x:
5 x - 10 = 3 x - 3 (x - 10)

-3 (x - 10) = 30 - 3 x:
5 x - 10 = 30 - 3 x + 3 x

3 x - 3 x = 0:
5 x - 10 = 30

Add 10 to both sides:
5 x + (10 - 10) = 10 + 30

10 - 10 = 0:
5 x = 30 + 10

30 + 10 = 40:
5 x = 40

Divide both sides of 5 x = 40 by 5:
(5 x)/5 = 40/5

5/5 = 1:
x = 40/5

The gcd of 40 and 5 is 5, so 40/5 = (5×8)/(5×1) = 5/5×8 = 8:

Answer: x = 8

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3.) Solve for x:
5 (x + 1) = 3 (2 x + 3) + 5

3 (2 x + 3) = 6 x + 9:
5 (x + 1) = 6 x + 9 + 5

Grouping like terms, 6 x + 5 + 9 = 6 x + (9 + 5):
5 (x + 1) = 6 x + (9 + 5)

9 + 5 = 14:
5 (x + 1) = 6 x + 14

Expand out terms of the left hand side:
5 x + 5 = 6 x + 14

Subtract 6 x from both sides:
(5 x - 6 x) + 5 = (6 x - 6 x) + 14

5 x - 6 x = -x:
-x + 5 = (6 x - 6 x) + 14

6 x - 6 x = 0:
5 - x = 14

Subtract 5 from both sides:
(5 - 5) - x = 14 - 5

5 - 5 = 0:
-x = 14 - 5

14 - 5 = 9:
-x = 9

Multiply both sides of -x = 9 by -1:
(-x)/(-1) = -9
(-1)/(-1) = 1:

Answer: x = -9