I believe this should work:
.full-width .contents .topic-list thead th.posts {
width: 10%;
}
.full-width .contents .topic-list thead th.activity {
width: 10%;
order: 4;
}
th.num.views {
width: 10%;
order: 3;
display: block;
}
.full-width .contents .topic-list tbody tr:not(.topic-list-item-separator) td.posts {
width: 10%;
order: 2;
}
.topic-list .views {
width: 10%;
order: 3;
}
.full-width .contents .topic-list tbody tr:not(.topic-list-item-separator) td.age {
width: 10%;
order: 4;
}