Correct option is (B) Book
Let the cost of 1 book, 1 pencil and 1 sharpener is Rs. x, y & z respectively.
\(\therefore\) According to given conditions
6x + 5y + 7z = 115 _________(1)
and 8x + 10y + 14z = 190 _________(2)
Multiply equation (1) by 2, we get
12x + 10y + 14z = 230 _________(3)
Subtract equation (2) from (3), we get
4x = 230 - 190 = 40
\(\Rightarrow\) x = \(\frac{40}4\) = 10 which is cost of 1 book.
From (2) given equations we can found only the value of x, because after substituting the value of x, we get two equations which are coincide. Therefore, we can not found the value of y & z.
Hence, only book's cost can be found uniquely.
