Beryllium Nitride has the formula Be3N2, and therefore has a molar mass of 55.06 grams per mole (you can use a periodic table to calculate this). By dividing 86 by 55.06, we can find the number of moles of Be3N2 present in this sample, which is equal to 1.562 moles.
86 g Be3N2 = 1.562 moles Be3N2