The document you've uploaded contains a set of one-step equations, followed by some word problems and expressions for simplification. Below, I'll solve the equations in sequence for clarity:

One-Step Equations:

1. x + 12 = 7

   • Solution: $x = 7 - 12 = -5$

2. 4 = -0.8n

   • Solution: $n = \frac{4}{-0.8} = -5$

3. 6 = -w/8

   • Solution: $w = 6 \times (-8) = -48$

4. 5/6 = 1/3 + d

   • Solution: $d = \frac{5}{6} - \frac{1}{3} = \frac{5}{6} - \frac{2}{6} = \frac{3}{6} = \frac{1}{2}$

5. x - 8π = π

   • Solution: $x = π + 8π = 9π$

6. -4/5 = -5/6k

   • Solution: $k = \frac{-4/5}{-5/6} = \frac{24}{25}$

7. 7x = 35

   • Solution: $x = 35 / 7 = 5$

8. -2 = 6/7n

   • Solution: $n = \frac{-2 \times 7}{6} = -\frac{14}{6} = -\frac{7}{3}$

9. 72 = -m

   • Solution: $m = -72$

10. r/π = 7.3

    • Solution: $r = 7.3π$

11. d - 2.8 ÷ 0.2 = -14

    • Solution: $d - 14 = -14 \implies d = -14 + 14 = 0$

12. m - (1/4) · 3 = -5/6

    • Solution: $m - 3/4 = -5/6 \implies m = -5/6 + 3/4 = \frac{-10 + 9}{12} = -1/12$

Word Problems:

13. Concert Ticket Problem:

    • Equation: $p - 14.50 = 53$
    • Solution: $p = 53 + 14.50 = 67.50$ (Original price of the ticket is $67.50)

14. Account Balance Problem:

    • Equation: $420 = \frac{7}{6} \times \text{Original balance}$
    • Solution: $\text{Original balance} = \frac{420 \times 6}{7} = 360$
    • Interest earned: $420 - 360 = 60$

Simplify the Expressions:

15. 4x + 9 - 6x - y

    • Simplified: $-2x + 9 - y$

16. 10 - 5(9n - 9)

    • Simplified: $10 - 45n + 45 = 55 - 45n$

17. -5n + 3(6 + 7n)

    • Simplified: $-5n + 18 + 21n = 16n + 18$

Extra Credit:

18. 12πx = 12π
    • Solution: $x = 1$

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Would you like further details on any particular question? Here are 5 related problems you might find interesting:

1. Solve: $3x + 5 = 17$
2. Simplify: $7(2x + 3) - 4x$
3. What is the original balance if 4/5 of it equals 320?
4. A discounted price is $25 less than the original price of $75. What's the original price?
5. If $a + b = c$, and $a = 5$, $c = 12$, what is $b$?

Tip: Always double-check your solution by substituting the variable back into the original equation to verify its correctness.