physical science 8th grade
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Copper has 2 known isotopes: ^63CU atomic mass= 62.9298 and ^65 CU atomic mass=64.9278. The average atomic mass of copper is 63.546 amu. Calculate the fraction(percent) of each of the 2 isotopes of copper

63.546=X*62.9298+ (1X)64.9278
where X is the decimal precent of Cu63, and 1x is the decimal percent of Cu65 
I am not understand