DAX code
Orders with Both Products =
VAR OrdersWithProductA = CALCULATETABLE(VALUES('Sales'[OrderID]), 'Product'[ProductName] = "Product A")
VAR OrdersWithProductB = CALCULATETABLE(VALUES('Sales'[OrderID]), 'Product'[ProductName] = "Product B")
RETURN
COUNTROWS(INTERSECT(OrdersWithProductA, OrdersWithProductB))