1. **State the problem:** Solve the system of equations:
$$-3x + 6y = 9$$
$$5x + 7y = -49$$
2. **Choose a method:** We will use the substitution or elimination method. Here, elimination is convenient.
3. **Eliminate one variable:** Multiply the first equation by 5 and the second by 3 to align coefficients of $x$:
$$5(-3x + 6y) = 5(9) \Rightarrow -15x + 30y = 45$$
$$3(5x + 7y) = 3(-49) \Rightarrow 15x + 21y = -147$$
4. **Add the two equations to eliminate $x$:**
$$(-15x + 30y) + (15x + 21y) = 45 + (-147)$$
$$\cancel{-15x} + 30y + \cancel{15x} + 21y = -102$$
$$51y = -102$$
5. **Solve for $y$:**
$$y = \frac{-102}{51} = -2$$
6. **Substitute $y = -2$ into one original equation to find $x$:** Using the first equation:
$$-3x + 6(-2) = 9$$
$$-3x - 12 = 9$$
$$-3x = 9 + 12 = 21$$
$$x = \frac{21}{-3} = -7$$
7. **Solution:** The solution to the system is $x = -7$, $y = -2$.
8. **Check the answer:** Substitute into the second equation:
$$5(-7) + 7(-2) = -35 - 14 = -49$$ which is true.
**Final answer:** $(-7, -2)$ which corresponds to option A.
Solve System 7Abd44
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.