I have three questions: 1. If I have a variable that is stored in a data set and I want to formulate only one constraint (under optmodel) that is a function of all the data set's observations of this variable and a decision variable. Suppose the variable is a and x is the decision variable. My constraint is: [(maximum value of a) +x ] / [(minimum value of a) +x ] < maximum value of (a) / minimum value of (a), can you help me to include this constraint under optmodel? 2. If there is one scalar number that is a result of certain calculations and the it is stored in a dataset and I want to equate a constraint with this scalar, can you help me to do this? 3. If there is one scalar number that is a result of certain calculations and it is stored in a dataset and I want to include this scalar in "sum" operator. Suppose there are also two stored variables that are a and b, and x is a decision variable and the scalar is c, I want c to appear as in the following constraint: sum over i for [ c*(ai)^2 * bi/ (ai+x)] = 0.5 , can you help me to do this under optmodel? Thanks Ayaa