Answer: 27, 28 and 29
Explanation:
Since the panels take three consecutive numbers of bolts to attach to the wall, let the numbers be y, y+1 and y+2.
y+y+1+y+2 = 84
3y+3=84
3y = 84 - 3
3y = 81
y = 27
Therefore, the bolts are 27, 28 and 29 respectively