Amy has total of 100 coins that are all dimes and quarters. The amount of money that equals is $21.40
Set up a system of equations and write the matrix equation that describes this situation. Let x = dimes
and y = quarters.

Question

Amy has total of 100 coins that are all dimes and quarters.  The amount of money that equals is $21.40 
Set up a system of equations and write the matrix equation that describes this situation.  Let x = dimes 
and y = quarters.

anonymous · Answer

x + y = 100
.10x + .25y = 21.4

anonymous · Answer

Do you know how to use substitution?

anonymous · Answer

Or did you just need the equations?

anonymous · Answer

i wouldnt know how to set it up

anonymous · Answer

x + y = 100 is the same as y = -x + 100
So put the value of y into the other equation and solve for x:
0.1x + 0.25(-x + 100) = 21.4
0.1x + -0.25x + 25 = 21.4
combine like terms:
-0.15x + 25 = 21.4
-25
-0.15x = -3.6
x = 24

Now plug the value of x into one of the original equations and solve for y:
x + y = 100
24 + y = 100
-24
y = 76

So this means you have 24 dimes and 76 quarters.
Hope I helped!