Answer :

2x(4x3+1) Is the answer
Hello, 

It is easy, you can descompose the number to do it easier:

26   |  2
13   |  13
  1

26= 2 * 13

We have 2, so, we have to get 13 with 1, 3 and 4

3*4 = 12
12+1 = 13

We got it, so the answer is:

2*[(3*4)+1]

Now, the excersice doesn't say that we can't put it together, so I think this can be another answer:

24+3-1=26