Using Dimensional Analysis
One mole of sillicon has a mass of 28.1 g, and one mole of oxygen has a mass of 16.0 . What is the mass of one mole of sillicon dioxide.
Si + O2 ==> SiO2
28.1 x (1 mol SiO2/1 mol Si) = 28.1 x (60.1/28.1) = 60.1
I suppose that's what is wanted for dimensional analysis; however, there is a quicker way to get it.
Simply add the atomic masses to obtain 28.1 + 2*16 = 60.1