Explanation:
this is an exercise to take the logical definition of an operation and apply it.
we have first a triangle operation that simply stands for the sum of the 3 included values divided by 3.
in other words, FYI, it creates the mean value of 3 given numbers.
so, we need to calculate
mean value (7, 4, 4) + mean value (8, 2, 11).
(7 + 4 + 4)/3 + (8 + 2 + 11)/3 = 15/3 + 21/3 = 36/3 = 12
the second calculation is based on a table defining a new operation Delta :
2 Delta 2 = 20
2 Delta 5 = 5
2 Delta 3 = 5
5 Delta 2 = 3
5 Delta 5 = 10
5 Delta 3 = 23
3 Delta 2 = 3
3 Delta 5 = 2
3 Delta 3 = 50
so, now we need to use this to calculate
(5 Delta 2) Delta (2 Delta 3)
3 Delta 5
2
the result is 2.