The total cost of 10 copies and 5 pens is 125 rupee. It is given that the cost (per unit) of two articles are 2 successive integers. Total cost of 1 copy and 1 pen is
According to the given condition
either 10x+5(x+1)=125
or 10(x+1)+5x=125
in one of the two cases x is not integer, so solve the other x=8
so answer = 8+9 = 17