I think we need more information. What is the purpose of combining the variables? It could be as simple as calculating a sum or product--that is a combination. It may be to find a principal component, sort of an underlying single variable that explains the bulk of the variation and covariance between the two variables. Without knowing the purpose, it is very difficult to offer a suggestion.
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.