M(раствора)=30,4+349,6=380г
w(FeSO4)=30.4*100%/380=8%
8%+25%=33%
30.4*100/(380-х)г=33
3040=33*(380-х)
3040=12540-33х
33х=12540-3040
33х=9500
х=9500/33
х=287,87878г=288г
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m1(раствора)=380-288=92г
m(Fe2SO4)=30.4г
w(FeSO4)=30.4*100%/92=33%
33%-8%=25%