This is two or more equations with common variables, also known as a linear system. System Of Equations
referendum
<span>A referendum is a direct vote in which an entire electorate is invited to vote on a particular legal proposal. the aim of the referendum is to approve or reject a certain law. Usually,referendum in most constitution are held on hot potato issues, or on amendment that seeks to amend the bills of rights or the system of governance.
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C i believe i might be wrong
Printing press that's the answer <span />