Solve the pair: 2x + 3y = 26 and x − y = -2. What is x?

Add or subtract the equations to eliminate one unknown, solve, then back-substitute. The correct answer is 4. Traps to avoid: -2 comes from the "gave x minus y" error; 10 comes from the "gave the sum" error; 28 comes from the "subtracted equations" error; 6 comes from the "solved for y" error.