Assuming one meal has been ordered for each person, let x and y represent the number of steaks and the number of chickens ordered, respectively. Then, we get the following system of linear equations. x + y = 12 (Eq. 1) 12x + 10.5y = 138 (Eq. 2) If we plug y = 12 - x, which is from Eq. 1, into Eq. 2, 12x + 10.5(12 - x) = 138 1.5x + 126 = 138 1.5x = 12 x = 8 and plug x = 8 into Eq. 1, we get y = 4. So, they ordered 8 steaks and 4 chickens.