double var_1 = double.Parse(project.Variables["var_1"].Value.Replace(".", ","));
double var_2 = double.Parse(project.Variables["var_2"].Value.Replace(".", ","));
double var_3 = double.Parse(project.Variables["var_3"].Value.Replace(".", ","));
double var_4 = double.Parse(project.Variables["var_4"].Value.Replace(".", ","));
double result = var_1 - (var_2 / var_3 * var_4);
result = Math.Round(result, 2);
return result.ToString().Replace(",", ".");