Solve for x.

3/8 = 12/x

x/5 = 10/12

4/6 = x/12

4/9 = 7/x

5/11 = 9/x

2/7 = x/21

7/8 = x/16

3/5 = 9/x

First one
remember
a/b=c/d also can be written as
ad=bc

so
first one can be rewritten as
3x=96
divide both sides by 3
x=32

2nd ones we can just times both sides by 5 to get
x=50/12

3rd one we times 12 both sides to get
x=8

4th one we translate to
4x=63
divide by 4
x=63/4

5th one we translate to
99=5x
divide by 5
99/5=x

6th one we times 21 both sides
6=x

7th one we times both sides by 16
14=x

last one we translate to
45=3x
divide 3
15=x

Answer: r=4.5  feetexplanation: radius  r  is half of the diameter  d,⇒r=d2=92=4.5  feetidk i could be wrong