Problem:

Range A1:G7 contains a table of the respective distances (miles) between 6 cities.
We want to use that table to retrieve the distance between each origin and destination pair shown in cells A10:B13.

Solution:

Use the INDEX and MATCH functions as shown in the following formula:
=INDEX($A$1:$G$7,MATCH(A10,$A$1:$A$7,0),MATCH(B10,$A$1:$G$1,0))