Answer
$50 \text{ miles}$
Work Step by Step
Distance = rate $\times$ time or $d=rt$
Therefore for each row,
Morning: $d= rt = 50x$
Afternoon: $d = rt = 40(x+\frac{1}{4}) = 40x+10$
She drives there in the morning, then drives back the same path in the afternoon.
Therefore, the distance for the morning and afternoon are equal.
Equate the distance to each other to solve for the variable $x$.
$50x = 40x+10\\
50x-40x = 10\\
10x =10\\
x=1$
Now we have $x$, put it into either equation to find the distance.
$d=50x\\
d= 50 \times 1\\
d=50 \text{ miles}$