A bag contains white marbles and yellow marbles, 78 in total. The number of white marbles is 2 less than 4 times the number of yellow marbles. How many white marbles are there?

There are 62 white marbles.

Step-by-step explanation:

Important information:

The number of white marbles is 2 less than 4 times the number of yellow marbles. 78 marbles in total.

Declare your variables:

Let w represent the number of white marbles.

Let y represent the number of yellow marbles.

Create your equations:

We know,

w = 4y - 2 (2 less than 4 times yellow)

w + y = 78 (total 78 marbles)

Solve:

We have an equation for w, so insert that into the second equation,

4y - 2 = 78

4y = 80

y = 16

Now we know the value of y, so insert that into the first equation,

w = 4 (16) - 2

w = 64 - 2

w = 62