2x³ - 13x² -kx + 105
since x - 7 is a factor, therefore x - 7 = 0 ; x = 7
Substitute the value for x in the equation.
i.e f(x) = 2x³ - 13x² -kx + 105
f(7) = 2(7)³ - 13(7)² - k(7) + 105
0 = 2(343) - 13(49) - 7k + 105
0 = 686 - 637 - 7k +105
0 = 154 - 7k
7k = 154
k = 154/7
k = 22
2x³ - 13x² -kx + 105
since x - 7 is a factor, therefore x - 7 = 0 ; x = 7
