If you travel at a constant speed, you follow this equation:
[tex] d = st [/tex]
where d is the distance, s is the speed and t is the time.
In this example, you first travel 60 miles per hour for 45 minutes. Since 45 minutes are 3/4 of a hour, you will cover a distance of
[tex] d_1 = 60\cdot\dfrac{3}{4} = 45 [/tex]
In the second part, since 30 minutes is half a hour, you will cover a distance of
[tex] d_2 = 50\cdot\dfrac{1}{2}=25 [/tex]
So, in total, you travel
[tex] d=d_1+d_2=45+25 = 70 [/tex] miles
