Respuesta :

Answer:

37.1

Explanation:

mass of 2 atoms of chlorine-35 = 2× 35 = 70

mass of 5 atoms of chlorine-38 = 5 × 38 =  190

average mass = total mass / total number of atoms

                        = (70 +190) / (2 +5)

                        =  260 / 7

                        = 37.143

                        = 37.1