Imagine the linear graphs of the 2 drivers, with distance y on the vertical axis and time t on the horizontal. The garage is where y = 0. Paul intersects the t axis at point X, where time t = 0.25 hours. Mary's line passes through the origin O. Both drivers intersect at point I. A lovely triangle OXI is born!

Anyway, the equations of each line are:

Paul: y = 60(t - 0.25) = 60t -15
Mary: y = 50t

where t is the absolute time from when Mary first passed the garage.

At point I, these are equal:

60t - 15t = 50t

So t = 1.5 hours since Mary passed the garage.

However Paul passed the gargage 0.25 h after Mary.

So answer = 1.5 - 0.25 = 1.25 h

D) 1 hour 15 mins.

Mary's Distance in 15 minutes = 50 * 15/60 = 12.5

Time to catch = 12.5/(10) = 1.25 ==> 1.25 * 60 = 75 minutes

Answer [spoiler]{D}[/spoiler]

Thanks team. When I missed this question I let the wording confuse me. I forgot to include the 2.5 miles that Mary drove, making the distance 12.5 miles as opposed to 10 miles. I chose C - 1 hour at first, but now understand that I needed the extra 15 mins to catch up.