Answer:
180 cm2 is the answer you can multiply all sides
calculate area of wall
20 x 1.5 = 30 square meters
now calculate area of 1 block
12 x 18 =216 square centimeters
convert cm to meters 1 cm^2 = 0.0001m^2
so 216 x 0.0001 = 0.0216 sq meter for 1 block
divide area of wall by area of block
30/0.0216 = 1388.88 so 1389 blocks are required.
