.library_pc {
	display:block!important;
}
.library_sp {
	display:none!important;
}
@media screen and (max-width:980px){
	  .library_pc {
		display:none!important;
	}
	  .library_sp {
		display:block!important;
	}
}
<div class="library_pc">
<div class="library_sp">