Alright, lets get started.
Suppose Tonya is driving at speed = x
As per given in question, Tonya drives 4 hrs, so distance covered by Tonya is :
[tex]distance = speed * time[/tex]
Distance covered by Tonya = 4x
Carmen drived half hour more than Tonya means carmen drived 4.5 hrs.
The speed of Carmen is also = x
So, distance covered by Carmen = 4.5 x
As per given in question, carman drives another half hour and goes 15 more miles.
It means, distance covered by Carmen is 15 more than distance covered by Tonya.
So putting it into equation,
[tex]4.5 x = 4x + 15[/tex] : Answer
Hope this will help :)