For the small tables, it will be 6X, because since they fit 6 people, you will need to multiply 6 times the amount of tables(which is X), then for the larger table, it will be 10Y, because since they fit 10 people, you will multiply 10 times the amount of tables (which is Y).
This leaves you with 6X+10Y
If they are expecting AT LEAST 150, then the equation needs to be set to greater than or equal to 150, but if they are expecting exactly 150, no more no less, then the equation will be set equal to 150.
Therefore it is either:
A: 6X+10Y>or=150
B:6X+10Y=150