Executive branch has the power to check the 
legislative branch by vetoing laws that Congress 
wants to pass
This provides a mastery of advantage over the Legislative branch by the Executive branch.
Legislative branch may check the executive branch 
by passing laws over the veto by two-thirds vote in 
each house
This provides a mastery of advantage over the Executive branch by the Legislative branch.
Judicial branch may check both the legislative and 
executive by declaring laws unconstitutional.
This provides a mastery of advantage over both the executive and legislative branches by the Judicial branch.
:)