Count the number of cubes in the given figure.

Clearly, there are 4 columns containing 1 cube each, 4 columns containing 2 cubs each and 1 column containing 3 cubes.

Hence, there are (4 x 1) + (4 x 2) + (1 x 3) = 4 + 8 + 3 = 15 cubes in the given figure.