If # means adding 9 times the second number to the first number, then (2 # 5) # 4 equals

51 27 83 59

83

# means adding 9 times the second number to the first number Let first number is A and 2nd  number = B So, A # B = A + 9B Now, (2 # 5) # 4 = (2 + 9 × 5) # 4 = (47) # 4 = 47 + 9 ×4 = 47 + 36 = 83