(will mark brainliest! ) a fictitious element x is composed of 70.0 percent of the isotope x^55, 20.0 percent of the isotope x^ 56, and 10.0 percent of the isotope x^57. calculate the weighted atomic mass of element x to the nearest tenth. you must show all of your work to earn credit.

We know that Weighted atomic mass of Element is Calculated based upon their existence of isotopes and the Relative abundance of these isotopes.

Given that the Element X is Composed of :

Isotope                       Relative abundance                   Atomic Mass

⁵⁵X                                        70%                                               55

⁵⁶X                                        20%                                               56

⁵⁷X                                        10%                                                57

Weighted Atomic Mass of Element X :

= (0.70)(55) + (0.20)(56) + (0.10)(57)

= 38.50 + 11.2 + 5.70

= 55.4

So, the Weighted Atomic Mass of Element X is 55.4