128.3 grams of methane (CH4) is equal to how many moles of methane

About 8.0 moles of methane. Number of moles = MassMolar mass.

And thus we get the quotient:

128.3⋅g16.04⋅g⋅mol-1=8.0⋅moles of methane.

Note that the expression is dimensionally consistent, we wanted an answer in moles, and the quotients gives, 1mol-1=11mol=mol as required.