1 2 x 1 2 )= 15 4 July 8, 2019 16 32 64 128 15 1 2 x 24 1 2 x 3 4 air filter 15 1 2 x 19 1 2 x 3 4 air filter 15 1 2 x 24 1 2 x 3 4 furnace filter 15 x 4 1 2 x 11 1 2 4 1 2 x 15 16 x 1 2 1 - 2 = 4 1 x 1 2 x 2
