This is stoichiometry, and I need to first make an equation, then balance it out and show the work of how I did it.. but I don't get how to do it..

The reaction 2C4H10 +13o2 = 8CO2+10H2O
so if 2 moles of C4H10 gives you 8 moles of CO2 then 1.7 moles of C4H10 gives you 6.8 molesof CO2
2-8
1.7-x
1.7*8/2
x=6.8