Solve the simultaneous equations: 2x + y = 18 and x - y = 6

We need to find a value of x to sub into equation 1, so add y to both sides of equation 2: x = 6 + y. Then sub this into the x value of equation 1 and solve to find y: 2(6 + y) + y = 18. 12 + 2y + y = 18. 3y + 12 = 18. 3y = 6. y = 2. To find the x-value, sub in this value of y into equation 2 and solve: x - (2) = 6. x = 8.