Let x, y and z be number of currency pieces of 5,10,20 rupees
x + y + z = 12 … (1)
5x + 10y + 20z = 105 … (2)
10x + 5y + 20z = 125 … (3)
Sub, z = 2 in (5), we get
15y + 20 x 2 = 85
15y = 45
y = 3
Sub; y = 3, z = 2 in (1)
x + y + z = 12
x = 7
∴ The solutions are
The number of Rs 5 are 7
The number of Rs 10 are 3
The number of Rs 20 are 2