Answer
120 minutes
Work Step by Step
It takes Hilda x minutes to finish work
It takes Stan 2x minutes to finish work (Hilda is twice as efficient)
Together it takes them 40 minutes
We will create equation from fractions of work they will do in one minute
$\frac{1}{x}$+$\frac{1}{2x}$=$\frac{1}{40}$
multipy by 40x
40+20=x
x=60
Stan: 2x=2(60minutes)=120 minutes
