Answer: 9 boys remained in the choir.
Step-by-step explanation:
Let x be the number of of boys and y be the number of girls.
In a school choir, 1/2(half) of the members were girls.
i.e [tex]x=y[/tex] (1)
At the end of the year, 3 boys left the choir, and the ratio of boys to girls became 3:4.
[tex]\dfrac{x-3}{y}=\dfrac{3}{4}\\\\\Rightarrow\ 4(x-3)=3(y)\\\\\Rightarrow\ 4x-12=3y[/tex]
Put y= x from (1), we get
[tex]4x-12=3x\\\\\Rightarrow\ 4x-3x=12\\\\\Rightarrow\ x=12[/tex]
Thus , the number of boys : x= 12
Boys remained in the choir = 12-3=9
