Answer: 7 hr
Step-by-step explanation:
Given
Distance between Emily and Kylie is [tex]140\ \text{miles}[/tex]
Speed of Emily [tex]v_e=12\ mph[/tex]
Speed of Kylie [tex]v_k=8\ mph[/tex]
Distance traveled by Emily [tex]\Rightarrow d_e=12t[/tex]
Distance traveled by Kylie [tex]\Rightarrow d_k=8t[/tex]
[tex]\Rightarrow 12t+8t=140\\\Rightarrow 20t=140\\\Rightarrow t=7\ hr[/tex]
They will meet after 7 hour.