Since the bottom shape is a semi-circle, the 3yd is the radius making the triangle's area 7 x 3 / 2 = 10.5
The semi-circle's area is

/2 = 14.14
Combined, you get an area of 10.5 + 14.14 = 24.64
1/4 to 1/2 percentage of change is 1/2
It has infinitely many solutions....because all real numbers satisfy the equation.
Good luck mate :P
16
Because...
4 cats/ 5dogs = x cats/ 20 dogs
Therefore you can conclude it is 16 cats in total