how to sum total in table vuejs

there are two rows of data row

<tr v-for="(data, index) in result_estimate.item_tabel" :key="index">
  <td>
    <pre> sub total : {{ambilaja(formatPrice(ambilPrice[index] - (ambilPrice[index] * subtotalRow[index])))}}</pre>
  </td>
<tr>
<div> total : {{this.totals}}</div>

the result of the above value is the total of each of each row, here I pass the value into the function ambilaja().

 return {
    totals : 0
    },
    computed : (){
         ambilaja: function(){
              return (value) => this.lempar(value)
         },
    }, 
    method : {
       lempar(data){
          console.log(data) 
          result console 
          30002 -> total row index 0
          2003 -> total row index 1
       }
    }

how to add up the total ? ex : 30002 + 2003 = this.totals