We know that volume of cuboid = length × breadth × height
Volume of the wall = 150 × 30 × 400 = 18000000 cm3
The quantity of mortar= 1/12 × 18000000 = 1500000
Volume of bricks= 18000000 – 1500000 = 16500000 cm3
Volume of single brick = 22 × 12.5 × 7.5 = 2062.5 cm3
Therefore, total number of bricks required
=total volume of the bricks/ volume of the each brick
= 16500000/2062.5
= 8000 bricks