a.
%35Cl=x; %37Cl=y
--->x+y=100
35x+37y=3550
--->x=75;y=25
---->%m35Cl =35.75/(35,5+16.3+1)=31,06%
b.
Fe : có 26p;30n;26e
p=n=1u ; e=0,00055 u
---->m(e)=(26.0,00055.1000/56)/(26.1+30+26.0,00055)=0,255g
c.
X1+X2+X3=87
X1.0,9223+X2.0,0467+X3.0,031=28,0855
X2-X1=1
--->X1,X2,X3