Solution:
Let x be the number of antifreeze solution. Thus;
[tex](0.4)x+1(5-x)=0.7x[/tex]We would solve for x;
[tex]\begin{gathered} 0.4x+5-x=0.7x \\ \\ 5=x-0.4x+0.7x \\ \\ 5=1.3x \\ \\ x=\frac{5}{1.3} \\ \\ x=3.85 \end{gathered}[/tex]Hence, the amount needs to be drained out is;
[tex]\begin{gathered} 5-x=5-3.85 \\ \\ =1.15 \end{gathered}[/tex]Answer: 1.15 gallon
