Answer:
40 tables total
Explanation:
Several ways to figure it out, but hopefully one of these is better for you to understand..
20 is half of 40 or 50% 50% in decimal form is .5 or .50 (either way works)
40 x .5 = 20 or you could say
1/2 of 40 is 20
So you would want to shade 20 tables, and the other 20 would be unshaded.