Awoman has 21 total coins in her pocket, all of which are either dimes or quarters. if the total value of her change is $3.90, how many dimes and how many quarters does she have? write the number of dimes, then the number of quarters separated by a comma.

Step-by-step explanation:

Givens

With this information we can construct a system of equations, where is dimes and is quarters.

, because there are 21 coins between dimes and quarters.

Now, we know that one dime values 10 cents, and one quarter values 25 cents.

, because the woman has $3.90 in total.

Then, we isolate in the first expression

And we substitute it in the second expression

Then, we use this value to find the other one

Therefore, the woman has 12 quarters and 9 dimes.

step-by-step explanation:

yes it represnts a functio, their are not 2 of the same numbers on the both sides

faster, im not sure why but i know it is faster