Coach South and Mr. Dr. Coach Rhodes are having a problem solving competition. Mr. Dr. Coach Rhodes can solve four more problems than twice the number of Coach South. If Mr. Dr. COach Rhodes has solved twenty problems, how many problems has Coach South solved?

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  8

Step-by-step explanation:

Let s represent the number of problems Coach South solved. Then Mr Dr Coach Rhodes solved ...

  2s +4 = 20

  2s = 16

  s = 8

Coach South solved 8 problems.

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional