Answer
3 hours
Work Step by Step
Karen: x
Betty: 6h
Together:$\frac{2}{3}$x
Fractions of work they will do in one hour:
Karen : $\frac{1}{x}$
Betty : $\frac{1}{6}$
Together : $\frac{1}{\frac{2}{3}x}$ = $\frac{3}{2x}$
Equation:
$\frac{1}{x}$+$\frac{1}{6}$= $\frac{3}{2x}$
multiply by 6x
6+x=9
x=3
