How many moles of h2o would be produced from 1.75 moles of o2 with unlimited c3h6

1.75 (moles O2) × 6 (moles H2O) ÷ 9 (moles O2) = 1.17 (moles H2O)

You have to convert moles of O2 into moles of H2O so it's the number of moles you start with (1.75 O2) × the number of moles from the element you want (6 H20), then ÷ by the number of moles that the element that you already have (9 O2).