pub template to include styles in head section

template.pug

doctype html
html(lang="en")
  head
    title= pageTitle
  //- link(rel="stylesheet" href="statement.css")
  style table td {
      |    border: 1px solid black;
      |  }
      | table {
      |   border: 2px solid #200e91; 
      | }
      | .summary thead {
      |   background: #d0d0e1
      | }
  body
    table(class="summary")
      thead
        tr
          td
            pre Summary of Your Account Activity                       
          td
      tbody
        tr
          td= `Previous Balance: ${stmt.previousBal}`
          td= `Account Name: ${info.card_number}`

To have a cleaner template, move styles to a css and link reference it (commented line able).