.outer-c {
    width:99%;
    margin-left:auto;
    margin-right:auto;
}

.sub_heading{
    font-size:16px; 
    color:purple; 
    margin-top:10px;
}

.three_groups{
    display:inline-block; 
    width:32%; 
    margin-right: 5px; 
}

@media (max-width:768px){
   
   .three_groups{
    display:block; 
    width:100%; 
    margin-right: 0px; 
}
   
    
}