A multinational army has a tank corps. Each tank requires a crew of two who speak a common language. Each possible crew member generally speaks more than one language. How might the problem of...

A multinational army has a tank corps. Each tank requires a crew of two who speak a common language. Each possible crew member generally speaks more than one language. How might the problem of maximising the number of crews be reduced to the problem of finding a maximum-cardinality matching for a graph in which each vertex

represents a possible crew member?