Answer:
[tex]Each\ of\ other\ two\ experiments\ required\ 3\ test\ tubes.[/tex]
Step-by-step explanation:
[tex]Let\ each\ of\ other\ experiment\ requires\ x\ test\ tube\\\\Total\ number\ of\ test\ tubes\ needed=8\\\\Test\ tubes\ used\ in\ the\ experiments=sum\ of\ number\ of\ test\ tubes\ in\ each\ experiment\\\\Test\ tubes\ used\ in\ the\ experiments=2+x+x\\\\2+x+x=8\\\\2+2x=8\\\\Subtract\ 2\ from\ both\ sides\\\\2+2x-2=8-2\\\\2x=6\\\\divide\ both\ sides\ by\ 2.\\\\x=3[/tex]
[tex]Each\ of\ other\ two\ experiments\ required\ 3\ test\ tubes.[/tex]