Question

PLEASE HELP SOMEONE. I WOULD REALLY APPRECIATE IT A newly discovered element, X, has two naturally occurring isotopes. 93.5 percent of the sample is an isotope with a mass of 268.9 u, and 6.5 percent of the sample is an isotope with a mass of 269.9 u. What is the weighted average atomic mass for this element?
268.5 u
269.0 u
269.8 u

Answer 1

Multiply mass(weight) with percent of abundance

(268.9 x 0.935) + (269.9 x 0.065) =

251.42 + 27.54 = 268.965 amu 

I moved the decimal two times to the left so that i don't have to divide by a 100 at the end.

Answer 2

269.0 u? I think I am not very Smart