question: How many decades had passed from the construction of the railway to the construction of the highway in Yucatan?
#1 return the  construction  of the   railway 
#2 return the  construction  of the   highway in  Yucatan 
#3 return when  was  #1 
#4 return when  was  #2 
#5 return difference of #4 and  #3 in  decades