Question 203169
Ok first you need to know the equ.s for speed, distance and time. 
Speed= distance x time 
Distance= speed/time
Time= speed/distance 

You need to figure out what distance this guy drove for at each speed and then add the together to find the total distance. 
Step one : 
Write down eq's for the two speeds but solving for distance
D1=x/3 then D2= (x+15)/2
D1+D2=Total distance 
We know x=45 so we sub 45 in for the all the x's and solve

D1=x/3            D2= (x+15)/2
  =45/3              = (45+15)/2
  =15miles           =30 miles
D1+D2= total
15 miles+ 30 miles= 45 miles
Therefore he travled 45 miles
** be sure to include all steps and units for full marks