Mary bought some bagels and some rolls. the bagels cost .40$ each and the rolls cost .25$. if she spent 3.90$ in all for 12 items, how many of each did she buy?

There are 6 bagels and 6 rolls.

Step-by-step explanation:

Let the number of bagels be 'b' and rolls be 'r'.

Given:

Cost of 1 bagel = $0.40

Cost of 1 roll = $0.25

Number of items = 12

Total cost of the 12 items = $3.90

Now, number of items is the sum of the bagels and rolls. So,

---------- (1)

Now, total cost of the items is the cost of 'b' bagels plus the cost of 'r' rolls.

So, total cost in equation form is:

--------- (2)

Now, multiplying equation (1) by -0.25 and adding the result to equation (2), we get:

So, number of bagels is 6.

Number of rolls,

So, there are 6 bagels and 6 rolls.