Answer:
She could prove that it is a combination of substances by looking for a change in color, or the formation of bubbles. She could also try to pull the combination apart by physical means alone.
Explanation:
207.217 amu
Work:
203.973 amu *(0.014) = 2.855 amu
205.974 amu *(0.241) = 49.639 amu
206.976 amu *(0.221) = 45.741 amu
207.977 amu *(0.524) = 108.979 amu
2.855 + 49.639 + 45.741 + 108.979 = 207.217 amu
