How to filter data from database based on Calculations?

Question

I tried to make a learning, and in learning there was a lesson. But I am confused about how to display the repeated data, I've tried it but it can't be displayed.

Next is the Controller

function daftarMatakuliahKontrak()
{
    $nim = Auth::guard('mahasiswa')->user()->nim;
    $khs = \DB::table('khs')
        ->where('khs.nim', $nim)
        ->get();

    foreach ($khs as $key) {
        $nilai = hitung_nilai($key->id);
        $kode_mk = ($key->kode_mk);

        if ($nilai < 60.0) {
            $ulang = \DB::table('khs')->where(kode_mk, $kode_mk)->get();
        } else {
            //Here if there are no repeated lessons
        }
    }
}

the following is a function to calculate values

function hitung_nilai($idKHS)
{
    $khs = DB::table('khs')
        ->where('id', $idKHS)
        ->join('matakuliah', 'matakuliah.kode_mk', '=', 'khs.kode_mk')
        ->first();

    $kontrak = \DB::table('kontrak')
        ->where('nidn', $khs->nidn)
        ->where('kode_mk', $khs->kode_mk)
        ->select('kontrak.kontrak_uts', 'kontrak.kontrak_uas', 'kontrak.kontrak_tugas', 'kontrak.kontrak_kehadiran')
        ->first();

    $uts = $khs->nilai_uts * ($kontrak->kontrak_uts / 100);
    $uas = $khs->nilai_uas * ($kontrak->kontrak_uas / 100);
    $tugas = $khs->nilai_tugas * ($kontrak->kontrak_tugas / 100);
    $kehadiran = $khs->nilai_kehadiran * ($kontrak->kontrak_kehadiran / 100);
    $hasil = $uts + $uas + $tugas + $kehadiran;

    // $jumlahbobot = $grade*'jml_sks';
    return $hasil;
}

and this JSON

{
    "kewirausahaan": {
        "kode_mk": "KM004",
        "nim": "15110185",
        "nilai_kehadiran": "80",
        "nilai_tugas": "90",
        "nilai_uts": "70",
        "nilai_uas": "86"
    },
    "Algoritma": {
        "kode_mk": "KM002",
        "nim": "15110185",
        "nilai_kehadiran": "50",
        "nilai_tugas": "60",
        "nilai_uts": "65",
        "nilai_uas": "60"
    }
}

Thanks for time