There are 21 marbles in a blue jar. the blue jars has 3 times as many marbles as a red jar. let m be the number of marbles in the red jar

m=7

Step-by-step explanation:

1 blue jar = 21 marbles

1 blue jar = 3 red jars

Therefor

21 marbles= 3 red jars

(Now let m=1 red jar)

21= 3m

(Then sine we have 3m dived both sides by 3 to isolate the m)

21/3= 3m/3

7=m

answer:

c. the third graph

is this part of a question or something