4 piglets, every 3 piglets are weighed together, and the weighing weight is 13 1 respectively. 145。 150。 138。 What is the average weight of these four piglets?
Number the four piglets from light to heavy, ABCD. From this set of figures, we can conclude that ABC plus 150, ABD plus 145, ACD plus 138, BCD plus 13 1. This is a system of quadratic linear equations. If you subtract the first one, the second one is C-D=5, the first one subtracts the third B-D= 12, and the first one subtracts the fourth A-D= 19. If d equals x, then A=X+ 19, B=X+ 12, and C =