The percentage increase; you'll need to take the new value and subtract it by the old value.
16 - 13 = 3
Next, you'll divide 3 by the original value.
3 ÷ 13 = 0.23
And multiply by 100
The percentage increase of friends is 23%
Answer to a : 30-19=x but for b i’m not that smart
Answer: 5
example:
4-2=2+8=10/2
=(2)
The volume would be 0.9 x 4.2
This means it is 90% smaller
Don't forget to round the nearest tenth place. That's the first decimal, so you answer should only have 2 digits.