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.

Which fact represents evidence for the big bang theory?

The element that has the greatest electronegativity is

Which of the following is most likely true about water in chemical systems? a) water dissolves nonpolar ionic compounds. b) water dissociates ionic compounds. c) water dissociates covalent molecules. d) water dissolves nonpolar covalent substances.