There are several different ways that Brad could arrange the blocks to create an array with the same number of blocks in each row. For example, he could create a 3x6 array by arranging the blocks into three rows of six blocks each. Alternatively, he could create a 6x3 array by arranging the blocks into six rows of three blocks each. He could also create a 2x9 array by arranging the blocks into two rows of nine blocks each. Or he could create a 9x2 array by arranging the blocks into nine rows of two blocks each
TL;DR: 3x6, 6x3, 2x9 and 9x2.