Answered!

curl -H "X-API-Key: $API_KEY" \
  "https://apiplay.net/api/v1/app?id=jawab.soal.matematika"

import requests

r = requests.get('https://apiplay.net/api/v1/app', params={'id': 'jawab.soal.matematika'},
                 headers={'X-API-Key': API_KEY}, timeout=30)
data = r.json()

const res = await fetch('https://apiplay.net/api/v1/app?id=jawab.soal.matematika', {
  headers: { 'X-API-Key': process.env.API_KEY },
});
const data = await res.json();

$ch = curl_init('https://apiplay.net/api/v1/app?id=jawab.soal.matematika');
curl_setopt_array($ch, [CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['X-API-Key: ' . getenv('API_KEY')]]);
$data = json_decode(curl_exec($ch), true);