First, we find the value of k(4). We can find the value of k(4) by substituting x = 4 in k(x).
Therefore the value of k(4) is 14. Next we find k(4)+k(4) which is equivalent to 14+14. Hence, the value of (k+k)(4) is 28. There's also another method.
As we know k(4) is 14. Therefore 2k(4) is 2×14 = 28.
Answer