Answer:
Explanation: the molar mass of the whole compound is 223.35u
now make ratios for each of the elements and multiply by 100%
copper= 63.55/223.35 x 100 % comp of copper is 28.45%
bromine= (79.9x2)/223.35 x 100 %comp of bromine is 71.54%
multiply bromines molar mass by 2 when calculating