The cross-price elasticity for left shoes and right shoes is expected to be positive because they are substitutes.
The cross-price elasticity of demand measures how the quantity demanded of one good responds to a change in the price of another good. In the case of left shoes and right shoes, since they are substitutes, we can predict that the cross-price elasticity would be positive. This means that if the price of left shoes increases, the demand for right shoes would also increase, and vice versa.