public static void Main()
string formula = "(cat1 + cat2 +(cat3*cat1)) / (cat3-cat1)";
formula = formula.Replace("cat1", cat1.ToString());
formula = formula.Replace("cat2", cat2.ToString());
formula = formula.Replace("cat3", cat3.ToString());
DataTable dt = new DataTable();
var v = dt.Compute(formula, "");
Console.Write(" = " + v);