GMAT Quantitative Reasoning Practice Test 3

Define $\mathit{X}$ as the average speed to the country club and $\mathit{Y}$ as the average speed on the way back.
The average speed of the entire round trip to the club is $87.5\%$ of the average speed on the way to the club: $(\mathit{X}+\mathit{Y}/2=0.875\mathit{X}$
$\mathit{X}+\mathit{Y}=1.75\mathit{X}$
$\mathit{Y}=0.75\mathit{X}.$
The average speed on the way back is $75\%$ of the speed to the club.
If the time it takes her to get to the country is $\mathit{T}$, then $\mathit{T}/0.75$ is the time it will take to get back home.
$50∕0.75=$ approximately66 minutes.