Hi Lexi;

*You have a collection of 50 marbles. Each one is red, white, or green. You have twice as many red marbles as green marbles. The difference between the number of white marbles and the number of red marbles is four less than the nember of green marbles. How many marbles of each color do you have?*

FIRST EQUATION...50=W+R+G

SECOND EQUATION...2G=R

THIRD EQUATION...G-4=W-R

Let's begin with the first equation...

50=W+R+G

Let's proceed with the third equation...

G-4=W-R

-4=W-R-G

Let's add the two equations together...

50=W+R+G

-4=W-R-G

46=2W+(0)R+(0)G

**23=W**

Let's return to the first equation...

50=W+R+G

50=23+R+G

Let's proceed with the second equation...

2G=R

Let's return to the first equation and substitute R with 2G...

50=23+2G+G

50=23+3G

27=3G

**9=G**

Let's return to the first equation...

50=W+R+G

50=23+R+9

50=32+R

**18=R**

Let's return to the first equation...

50=W+R+G

50=23+18+9

50=50

Let's return to the second equation...

2G=R

(2)(9)=18

18=18

Let's return to the third equation...

G-4=W-R

9-4=23-18

5=5