Explanation:
are you sure you for everything correctly ?
to me this gives the impression that there are some things potentially missing.
what I can see :
26 - (6 + 6) + 3(23 - 8)
remember the priorities of mathematical operations :
1. brackets
2. exponents
3. multiplications and divisions
4. additions and subtractions
so we need to start with the brackets :
26 - (12) + 3(15) = 26 - 12 + 3×15
now we need to do the multiplication
26 - 12 + 45
and not the additions and subtractions
26 - 12 + 45 = 59
we had no exponents anywhere, so, we could skip 2.