Review of Chapter 8: Solving A System of Linear Equations

From class, we had the problem: 3x + (1/3)y = 10; 2x - (5/3)y = 35. So, multiply 3 to everything. So, 3(3x + (1/3)y = 10); 3(2x - (5/3)y = 35). Therefore, you have 9x + y = 30; 6x - 5y = 105, respectively. Now, multiply the first linear equation by 5:5(9x + 5 = 30). So, 45x + 5y = 150; 6x - 5y = 105. Add them, and you get, 51x = 255. Therefore, x = 5. Using the second equation, plug in 5 for x. So, 3(5)+(1/3)y = 10. Therefore, 15 + (1/3)y = 10. Solve for y. So, (1/3)y = -5. Then, multiply each side by 3. So y = -15. QED