Answer :

2 hours! This is because she's driving 40 mph and has to drive 80 miles so 80/40= 2
[tex]v=40\ mph\\\\s=80\ miles\\\\t=?\\--------------\\v=\frac{s}{t}\to vt=s\to t=\frac{s}{v}\\--------------\\t=\frac{80\ miles}{40\ mph}=2\ h\leftarrow Answer[/tex]