Hello! So the blocks are lined up in rows of 8. When you count the number of rows, there are 10 of them. 3 rows of 8 blocks are shaded out of 10 of them. That's 24 blocks shaded out of 80, because 8 * 10 is 80, and 3 * 8 is 24. Let's divide. 24/80 is 0.3.Let's multiply that by 100 to get it in percent form. 0.3 * 100 is 30. There. 30% of blocks are shaded in the picture.
