Question 565171
Snowplow speed be x

in 2 hours before the car starts it has traveled 2x miles

Catch up distance = 2x
catchup time = 1/2 hour
catchup rate = 30-x  ( since they are travelling in same directions

2x/(30-x)=1/2

cross multiply
4x=30-x
4x-x=30
2x= 30
/2 
x=15 mph---- speed of snowplow