A 8.18 g sample of copper is contaminated with 0.90 g of zinc. Suppose an atomic mass measurement was performed on this sample. What would be the measured atomic mass? Express your answer to four significant figures and include the appropriate units.
Ok so far the answer that I've been getting was 70.54 g, which isn't right according to my online homework. I got that answer by doing this: (0.90*63.55)/8.18, which got me 6.99. I then added this to 63.55 and got 70.54. What am I doing wrong?