Let x% be the salt concentration of first solution.
Then in 8ml, amount of salt = [tex]\frac{8x}{100}[/tex]
Given that to this 8ml solution, 11ml solution of a 47% salt solution is mixed.
amount of salt in 11ml of 47% salt solution is [tex]\frac{11*47}{100}[/tex] = [tex]\frac{517}{100}[/tex]
So, total amount of salt in new mixture = [tex]\frac{8x}{100} +\frac{517}{100} = \frac{8x+517}{100}[/tex]
But given that this new solution is a 43% salt solution.
Hence amount of salt in new mixture of (8+11)=19ml solution of 43% salt solution is [tex]\frac{19*43}{100} = \frac{817}{100}[/tex]
Hence [tex]\frac{8x+517}{100} = \frac{817}{100}[/tex]
8x+517 = 817
8x=817-517 = 300
x= 300/8 = 37.5
Hence the salt concentration in the first solution is 37.5%