Question

If Joe used 20 coins worth $2.60 to wash 4 loads, how many of each coin did he use?

Answer 1

We have

Quarter =.25

Nickel= =.05

x= number of quarters

y= number of nickels

the first equation is

x+y=20

The second equation is

.25x+ 0.05y=2.60

Then we solve the system of equation , with the first equation we isolate the x

x=20-y

then we substitute the equation above in the second equation

.25(20-y)+ 0.05y=2.60

We sum similar terms

`\begin{gathered} 5-.25y+0.05y=2.60 \\ 0.3y=2.60-5 \\ y=(-2.4)/(-0.2) \\ y=12 \end{gathered}`

we substitute the value of y in the equation with x isolate

`x=20-12=8`

therefore the answer is

8 quarters and 12 nickels