What is the command using * ngIf to do a larger and smaller check

I recommend using ngClass instead of ngIf to dynamically style your components. Let's imagine a scenario where you have several styles, you would have to make several identical components just changing their style, this is bad practice because you are repeating code.

Example:

<p [ngClass]="getClass()">{{resultado.mediaTotal}}</p>

Note that we are not doing any validation in html, we can leave that part pro component , where in this example I created the function getClass()

In your Component / Page you would do something like:

 getClass(){
    if(this.resultado.mediaTotal > 50 && this.resultado.mediaTotal < 70)
      return 'my-style-green'
    if(this.resultado.mediaTotal < 50)
      return 'my-style-red'
  }

Note that it is returning a string, this string is your class you can put in the css of your page.

.my-style-green{
     color: green;
 }
 .my-style-red{
     color: red;
 }

You should use the logical operator &&

<p 
    *ngIf="resultado.MediaTotal > 50 && resultado.MediaTotal < 70"
    style="color:green">
        {{resultado.MediaTotal}
</p>