Question 459884
distance to school = x	km						
Motorbike time =x/20				
Bicycle time  =x/12				
Difference in time =13/60 =0.22	hour 
Bicycle time - motorbike time = 0.22			
x/12-x/20=0.22	
							
common denominator = 	240						
multiply by LCD							
20x-12x=0.22*240
8x=52.8					
/8						
x=6.6 km