Answer: She has 13 dimes and 37 nickels.
Explanation:
We know that
1 dollar = 100 cents
Then, the value of one dime =10 cents =$0.1
and the value of one nickel = 5 cents = $0.05
Given : Elizabeth has 50 coins in nickels and dimes only and has a total of $3.15.
Let x be the number of dimes and y be the number of nickels , then the required system of equation would be :-
![x+y=50------------------(1)\\\\ 0.1x+0.05y=3.15----------------(2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/l9rcmf7za3vwh8lfv06mhs65nrf63lz9b4.png)
Multiply 10 to eqn (2), we get
![x+0.5y=31.5---------------------(3)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pvz7w2dwkeiejqrhvhfyb4ue3r4i7jo9gn.png)
Subtract eqn (3) from eqn (1), we get
![0.5y=18.5](https://img.qammunity.org/2020/formulas/mathematics/middle-school/xg6um94a39vbb8nnkznmqeygo9l5xciiml.png)
Divide both sides by 0.15, we get
![y=(18.5)/(0.5)=37](https://img.qammunity.org/2020/formulas/mathematics/middle-school/csqwmnhjtszcoao8lbzjnggeagbx6hxeg5.png)
Put value of y in (1), we get
![x+37=50\\\\ x=50-37=13](https://img.qammunity.org/2020/formulas/mathematics/middle-school/t1m999ozaiwo0g6mrs3hambe10lqh91zjz.png)
Therefore, she has 13 dimes and 37 nickels.