Question

Imagine having 20 currency notes , consisting of $5 bills , and $10 bills that total $125. Write a system of equations to describe the situation.

Answer 1

X-the $5 bills 
y-the $10 bills

x+y=20
5x+10y=120  

It's a system.

Answer 2

Hi,

Reading the problem you can understand that you have 20 currency notes. So, all the currency notes (5 and 10) summed are 20.

Now, you know that there are some 5 and 10 bills of these, but you don't know how many of these are $5 or $10...you only know that summing all these bills give $125.

Setting a sistem of linear equation would be like this:

i call x the $5 bills and y the $10 bills.

x+y = 20
5x + 10y = 125

The final results are x = 15 and y = 5

Hope it is clear!