.main-class{
       .page-title-wrapper{
         width: calc( 100% - 45px );
       }
 }

.main-class  .page-title-wrapper{
     width: calc( 100% - 45px );
 }

.main-class  .page-title-wrapper{
     width: calc( 55%);
 }

.main-class{
       .page-title-wrapper{
         width: calc(~"100% - 45px");
       }
 }