Given,
The perimeter of the triangle, p=17 inches
Length of the 1st side of the triangle, a=5 inches
The length of the other side of the triangle, b=4 inches.
Let the other side of the triangle be c.
The perimeter of the triangle is given by,

Therefore the value of the third side, c can be calculated as,

On substituting the known values in the above equation,

Therefore, the length of the third side is 8 inches.
And the correct answer is option B.