A bag contains 21 coins consisting of nickles and dimes. The total value of the coins is $1.70. Write a system of equations that models this situation. How many nickels are in the bag?

8

Step-by-step explanation:

x = nickles

y = dimes

0.05x + 0.10y = 1.70

x + y = 21

y = 21 - x

0.05x + 0.10 (21 - x) = 1.70

0.05x - 0.10x + 2.10 = 1.70

-0.05x + 2.10 = 1.70

-0.05x = -0.40

x = 8

(0,-3) see attached graph

step-by-step explanation:

a. to solve the system, graph the two equations.

x = y+3 becomes y=x-3 has m=1/1 and b=-3. start at (0,-3) on the y-axis and plot a point. then move up 1 unit and 1 unit to the right. plot a point and connect.

y=-4x+3 has m =-4/1 and b=-3. start at (0,-3) on the y-axis and plot a point. then move down four units and to the right 1 unit. plot a point and connect.

the solution is the point (x,y) where the two lines intersect. by the graph below it is (0,-3).

b. to solve by substitution, substitute y = -4x-3 into x= y+3

x= (-4x-3) +3

x=-4x

5x=0

x=0

now substitute x = 0 back in to find y.

y= -4(0)-3

y=0-3

y=-3

solution is (0,-3)

c. use elimination by adding the equations together.

x-y=3

4x+y=-3

5x=0

x=0

then substitute into one equation to find y.

y=-4(0)-3

y=-3