Please help me with question b) and please explain!!
look at the attached image

17

Step-by-step explanation:

let x be the number of boxes to be shaded to make it 80%

x = 80% of total number

= 80/100 of 25

= 80/4

= 20

So 20 need to be shaded to fill 80%

Now, 13 of the grids are already shared so the amount of more squares that need to be shaded = 20-13

= 17 squares