Question: how to calculate zj in simplex method?
Answer: The new zj row values are obtained by multiplying the cB column by each column, element by element and summing. For example, z1 = 5(0) + -1(18) + -1(0) = -18. The new cj-zj row values are obtained by subtracting zj value in a column from the cj value in the same column. For example, c1-z1 = 12 - (-18) = 30.