Answer:
Emily can see Emerson for 15 minutes.
Step-by-step explanation:
As the values of speed and distance are missing in given question so we consider complete statement attached in Figure below.
Speed of Emily = 12 mile/hr
Speed of Emerson = 8 mile/hr
Speed of Emily relative to Emerson = 12 - 8 = 4 mile/hr
Initial distance between them = 1/2 mile
After crossing Emerson, distance between them = 1/2 mile
Time for which we can see Emily is moving with relative constant speed (Vr) of 4 mile/hr and Emerson is not moving at all relative to her
[tex]=\frac{Dist}{V_{r}}\\\\=\frac{\frac{1}{2}}{4}\\\\=\frac{1}{8} hrs[/tex]
Total distance in which Emily can see Emerson = 1/2 + 1/2 = 1 mile
Time spend in reaching Emerson covering 1/2 mile = 1/8 hrs
Time Emily can see Emerson in rear mirror for 1/2 mile = 1/8 hrs
Total time [tex]=\frac{1}{8}+\frac{1}{8}[/tex]
[tex]=\frac{1}{4} hrs\\\\=\frac{1}{4} (60 mins)\\\\=15 mins[/tex]
