A sample of unknown element X contains the following isotopes: 80% of C -64, 15% of X - 65, and 5% of X-66. What is the average atomic mass of element X? Can somebody help me with this question. Will mark brainliest.

Answer:
64.25
Explanation:
Average atomic mass = percentage × mass of all isotopes/ 100
Relative atomic mass = 80*64+15*65+5*66/100
=5120+975+330/100
=6425/100
64.25