we know that
speed=distance/time------> distance=speed*time
step 1
find the distance with
speed=30 miles/hour-----> 30 miles/60 minutes-----> 0.5 miles/minute
time=12 minutes
distance=speed*time------> distance=0.5/12----> distance=6 miles
the distance from home to school is 6 miles
step 2
find the speed with
distance=6 miles
time=18 minutes
speed=6/18----> 0.33 miles/minute-----> *60----> 20 miles/hour
the answer is
20 miles/hour or 0.33 miles/minutes