X+Y+Z = 36000

Y = Z+11000

0.03X + 0.04Y + 0.05Z = 1490

===== substitutes second equation into first and third equations =================

X + Z+11000 + Z = 36000

0.03X + 0.04(Z + 11000) + 0.05Z = 1490

**X + 2Z = 25000**

X = 25000 - 2Z

0.03X + 0.09Z + 440 = 1490

**0.03X + 0.09Z = 1050**

0.03( 25000 - 2Z) + 0.09Z = 1050

750 - 0.06Z + 0.09Z = 1050

750 + 0.03Z = 1050

0.03Z = 300

3Z = 30000

Z = 10000

Y = 21000

X = 5000