def adjust_age_groups(age_labels):
    """
    for each pair of cols to aggregate, takes the first number of the first element, and the last number for the last element
    for instance: ["0-4",'5-10'] -> ['0-10']
    """
    i=0
    new_age_labels=[]
    label=""
    for element in age_labels:
        if i%2==0:
            label+=element.split('-')[0]
            i+=1
        elif i%2==1:
            label=label+'-'+element.split('-')[-1]
            new_age_labels.append(label)
            label=""
            i+=1
    #making the last agegroup based on the first number +
    new_age_labels[-1]= new_age_labels[-1].split("-")[0]+"+"
    return(new_age_labels)