title: Angular *ngIf expression with number and string concatenation
body: <p>I have a div with <code>*ngIf=&quot;agreement.errors?.required&quot;</code> and I also have an index defined as <code>i</code>.</p>
  <p>I want to add the value of the index  or <code>i</code> to the word agreement before evaluating the overall value of <code>&quot;agreement&lt;i&gt;.errors?.required&quot;</code>.</p>