Respuesta :

Explanation:

Difference between 63 and 65 = 2.

(63.55 - 63) / 2 * 100% = 27.5%.

(65 - 63.55) / 2 * 100% = 72.5%.

Hence there is 72.5% of the isotope with atomic mass 63 and 27.5% of the isotope with atomic mass 65 in copper.