1. Problem 21: Given the equation $y = 3x - 2$, find $y$ when $x = 10$. 2. Substitute $x = 10$ into the equation: $$y = 3(10) - 2$$ 3. Calculate: $$y = 30 - 2 = 28$$ 4. Problem 22: Given $y = 3x - 2$, find $x$ when $y = 13$. 5. Substitute $y = 13$: $$13 = 3x - 2$$ 6. Add 2 to both sides: $$13 + 2 = 3x$$ $$15 = 3x$$ 7. Divide both sides by 3: $$\frac{\cancel{15}}{\cancel{3}} = \frac{3x}{3}$$ $$5 = x$$ 8. Problem 23: Sketch the line $y = 2$. 9. This is a horizontal line crossing the y-axis at 2. It runs parallel to the x-axis. 10. Problem 24: Solve $\frac{x}{5} = \frac{4}{3}$. 11. Cross multiply: $$3x = 5 \times 4$$ $$3x = 20$$ 12. Divide both sides by 3: $$\frac{\cancel{3x}}{\cancel{3}} = \frac{20}{3}$$ $$x = \frac{20}{3}$$ 13. Problem 25: Solve $-2 = \frac{3}{x}$. 14. Multiply both sides by $x$: $$-2x = 3$$ 15. Divide both sides by $-2$: $$x = \frac{3}{-2} = -\frac{3}{2}$$ 16. Problem 26: Solve $3x = 1 - \frac{x+5}{2}$. 17. Multiply both sides by 2 to clear the denominator: $$2 \times 3x = 2 \times \left(1 - \frac{x+5}{2}\right)$$ $$6x = 2 - (x + 5)$$ 18. Simplify the right side: $$6x = 2 - x - 5$$ $$6x = -x - 3$$ 19. Add $x$ to both sides: $$6x + x = -3$$ $$7x = -3$$ 20. Divide both sides by 7: $$x = \frac{-3}{7}$$