-7,7:(1+(-5,8):(26:(-13))

First, let's calculate the innermost parentheses:
26:(-13) = 26 / (-13) = -2

Now we can substitute -2 back into the equation:
-7,7:(1+(-5,8):-2

Next, let's calculate the addition within the parentheses:
1 + (-5,8) = 1 - 5.8 = -4.8

Now we can substitute -4.8 back into the equation:
-7,7:(-4.8):-2

Finally, let's divide -4.8 by -2:
-4.8 / -2 = 2.4

Therefore:
-7,7:(1+(-5,8):(26:(-13)) = 2.4