diketahui harga 3 baju dan 2 kaos Rp280.000,00 ,sedangkan harga 1 baju dan 3 kaos Rp210.000,00 ,tentukanlah hasil kali kedua bilangan itu

baju = x
kaos = y

3x+2y=280rb [x1]
x+3y=210rb [x3]

3x+2y=280rb
3x+6y=630rb
___________ -
-4y=-350rb
y=-350rb : -4
y= 87,500

x+3y=210rb
x+3(87,500)=210,000
x+262,500=210,000
x=210,000-262,500
x=-52,500

jadi,
baju=-52,500
kaos=87,500

x+3y=210,000
(-52,500)+3(87,500)=210,000
(-52,500)+262,500=210,000