Shared Solution
1. **State the problem:** We have three equations:
$$y = -2$$
$$y = x + 3$$
$$y = -2x - 12$$
We need to find their shared solution (the point where all three lines intersect).
2. **Find intersection of the first two lines:**
Since $$y = -2$$, substitute into $$y = x + 3$$:
$$-2 = x + 3$$
Solve for $$x$$:
$$x = -2 - 3 = -5$$
So the intersection is at $$(-5, -2)$$.
3. **Check if this satisfies the third equation $$y = -2x - 12$$:**
Substitute $$x = -5$$:
$$y = -2(-5) - 12 = 10 - 12 = -2$$
This matches the $$y$$ value.
4. **Therefore, the shared solution of the first three equations is:**
$$\boxed{(-5, -2)}$$
5. **Part b: Find $$c$$ in $$y = 3x + c$$ that shares this solution:**
Substitute $$x = -5$$ and $$y = -2$$ into the equation:
$$-2 = 3(-5) + c$$
$$-2 = -15 + c$$
Solve for $$c$$:
$$c = -2 + 15 = 13$$
6. **Answer:**
$$c = 13$$
**Final answers:**
- a) Shared solution: $$(-5, -2)$$
- b) Value of $$c$$: $$13$$