[douglas]

Robotoid + Mineral Scanner = 45% increase (only better value works)
System Robotoid + System Mineral Scanner = 45% increase (only better value works)
Robotoid + System Robotoid = 69% (stack multiplicatively)
Robotoid + System Mineral Scanner = 88.5% increase
Mineral Scanner + System Robotoid = 88.5% increase
Mineral Scanner + System Mineral Scanner = 110.25% increase

Note that the increase from system-wide facilities will not be shown on the individual planets. The only figure the game displays that includes that bonus is the empire-wide total.