HBr molar mass is 80.9 g/mol this means in 80.9 g - 1 mol of HBr 1 mol consists of 6.022 x 10²³ molecules of HBr that means in 80.9 g HBr there are 6.022 x 10²³ molecules of HBr therefore in 42.5 g of HBr there are 6.022 x 10²³/80.9 * 42.5 the number of HBr molecules are therefore - 3.16 x 10²³ HBr molecules
