JSFiddle - React, Tailwind, and code Playground
HTML
<script src="https://rawgit.com/eu81273/jsfiddle-console/master/console.js"></script>
JavaScript
let valorKg = 9.9;
let peso = +prompt('Quantos kilos foram pescados?');
let valorSemDesconto = 0;
let valorFinal = 0;
valorSemDesconto = peso * valorKg;
if (peso > 2.9){
valorFinal = valorSemDesconto * 0.95;
}else{
valorFinal = valorSemDesconto;
}
console.log(`Valor final: ${valorFinal}`);