3. Anita membeli 3 buku tulis, 1 bulpoin, dan 2 spidol seharga Rp.14.500,00. Bella membeli 1 buku tulis dan 3 bulpoin seharga Rp.7500,00. Cindi membeli 2 bulpoin dan 3 spidol seharga Rp.9000,00. Berapakah uang yang harus dibayar Dina jika dia membeli 2 buku tulis, 2 bulpoin, dan 1 spidol

<p><strong>Diketahui:</strong><br>x = buku tulis<br>y = bolpoin<br>z = spidol<br><br><strong>ANITA</strong><br>3x + y + 2z = 14.500 ....(1)<br><strong>BELLA</strong><br>x + 3y = 7.500.....(2)<br><strong>CINDI&nbsp;</strong><br>2y + 3z = 9.000.....(3)<br><br><strong>Ditanyakan:&nbsp;</strong><br><strong>DINA&nbsp;</strong><br>2x + 2y + 1z =?<br><br><strong>Solusi:</strong><br><strong>Metode Eliminasi Substitusi</strong><br><strong>Pers (1) dan (2)</strong><br>3x + y + 2z = 14.500&nbsp;<strong> (Kali</strong> <strong>1) &nbsp;</strong>3x + y + 2z = 14.500<br>x + 3y = 7.500 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<strong>(Kali 3) &nbsp;</strong><u>3x + 9y = 22.500 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</u> _<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;-8y + 2z = -8000 &nbsp;kali (-)<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;8y - 2z = 8000 &nbsp; &nbsp;bagi 2<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<strong>4y - z = 4000 .....(4)</strong><br><strong>Pers (3) dan (4)</strong><br>2y + 3z = 9.000 <strong>(Kali</strong> <strong>2) </strong>4y + 6z = 18.000<br>4y - z = 4000 &nbsp; &nbsp; &nbsp;<strong>(Kali</strong> <strong>1) </strong><u>4y - z = 4000 &nbsp; &nbsp; &nbsp;&nbsp;</u> _<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 7z = 14000<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;<strong> z = 2000</strong><br><br><strong>Substitusi z = 2000 ke pers (3)</strong><br>2y + 3z = 9.000<br>2y + 3 (2000) = 9000<br>2y + 6000 = 9000<br><strong>y = 1500</strong><br><br><strong>substitusi y = 1500 ke pers (2)</strong><br>x + 3y = 7.500<br>x + 3(1500) = 7500<br>x + 4500 = 7500<br><strong>x = 3000</strong><br><br>Jadi yang dibayar DINA adalah<br>2x + 2y + 1z = 2 (3000) + 2(1500) + 1(2000) =<strong> 11000</strong></p>