Answer: 30%
Step-by-step explanation:
Ignore the horizontal lines. Think of this figure as 10 skinny rectangles line up side by side. Three of them are shaded, so we have 3/10 = 0.30 = 30% of it shaded.
If you wanted to include the horizontal lines, then we have 10*3 = 30 green little squares out of 10*10 = 100 total squares. This leads to the same answer 30/100 = 0.30 = 30%