A bag contains 150 marbles. Some are blue, and the rest are white. There are 21 blue marbles for every 4 white marbles. How many blue marbles are in the bag? Explain your reasoning.

Given:

Total number of marbles in the bag = 150

There are 21 blue marbles for every 4 white marbles.

To find:

The number of blue marbles in the bag.

Solution:

Since, there are 21 blue marbles for every 4 white marbles, therefore the ratio of blue marble to white marbles is 21:4.

Let the number of blue marbles be 21x and white marbles be 4x.

Total number of marbles in the bag = 150

Divide both sides by 25.

Now,

Therefore, the number of blue marbles is 126.

option 3 . (5x + 1) - (-10x + 6)

step-by-step explanation:

option 1 :

(4x + 3) + (-9x + 4)

or 4x+3 -9x + 4

or -5x + 7

option 2

(x - 2) - (6x - 9)

or x-2-6x + 9

or -5x + 7

option 3

(5x+ + 6)

or 5x + 1 + 10x -6

or 15x -5

option 4

-4x+2x+7-3x

-7x + 2x + 7

-5x + 7

hence only option 3 did   not satisfy the given simplify expression.