A bag contains green marbles and blue marbles, 24 in total. The number of green marbles is 6 less than 2 times the number of blue marbles. How many green marbles are there?

Answer 1

You have to write out an equation in order to find out how many green marbles are in the bag.

Blue will be represented with x

Green is written out as 6 less than 2 times the number of blue

less than means subtraction

2 times the number means multiplication

2x - 6

Now put it together then solve for x:

2x - 6 + x = 24

3x - 6 = 24

3x = 30

x = 10

The question asked you to find the number of green marbles. Substitute 10 in for x to get the number of green marbles.

2(10) - 6 = 14

I hope this helps you.

Answer 2

g + b = 24

g = 2b - 6

I see two quick ways to solve this. The first is simply to substitute the given "value" of g in the 2nd equation for g in the first equation.

2b - 6 + b = 24

3b - 6 = 24

3b - 6 + 6 = 24 + 6

3b = 30

3b/3 = 30/3

b = 10

g = 2(10) - 6

g = 20 - 6

g = 14

Another way I see quickly is to solve the 1st equation for g.

g = 24 - b

Now, if g = 24 - b and g = 2b - 6, then...

24 - b = 2b - 6

24 - b - 2b - 24 = 2b - 6 - 2b - 24

-3b = -30

-3b/-3 = -30/-3

b = 10

g = 2(10) - 6

g = 20 - 6

g = 14