Question

A SAMPLE OF ANTIMONY, Ar=121.8, WAS ANALYSED AND WAS FOUND TO CONSIST OF 60% OF 121Sb AND ONE OTHER ISOTOPE. DETERMINE THE MASS NUMBER OF THE OTHER ISOTOPE IN THE SAMPLE OF ANTIMONY.

please help I'm really stuck,
bobpursley
assume you have 100 grams. It becomes the overused algebra candy mixture problem.

60*121+40*X=121.8*100
solve for x
Dannau
Thats wrong. The answer is 123
0oooooooo0
How do you get that though
Muhammad
121.8=(0.6*121)+(0.4*x)
121.8=72.6+0.4x
49.2=0.4x
x=123