Solve for x in the following equations: a) 6x = 72, b) 7x = 84. Solve for x in the following equations: a) 5x − 6 = 18, b) 3x + 4 = -5. Substitute the given values into the equations: a) y = p2 + 7; p

$$x = 12$$

The solution is $\boxed{x = 12}$.

b) $7x = 84$

$$x = 12$$

The solution is $\boxed{x = 12}$.

8. Solve for $x$.

a) $5x - 6 = 18$

$$5x - 6 + 6 = 18 + 6$$ $$5x = 24$$

$$x = \frac{24}{5} \quad \text{or} \quad x = 4\frac{4}{5}$$

The solution is $\boxed{x = \frac{24}{5}}$.

b) $3x + 4 = -5$

$$3x + 4 - 4 = -5 - 4$$ $$3x = -9$$

$$x = -3$$

The solution is $\boxed{x = -3}$.

9. Substitute.

a) $y = p^2 + 7$; $p = 8$

$$y = 71$$

The value of $y$ is $\boxed{y = 71}$.

b) $y = c^2 + 4$; $c = 5$ (assuming $c=5$ from the visible part of the question)

$$y = 29$$

The value of $y$ is $\boxed{y = 29}$.