A mother earned $8750 from royalties on her cookbook. She set aside 20% of this for a down payment on a new home. The balance will be used for her son's future education. She invests a portion of the money in a bank certificate of deposit (CD account) that earns 4% and the remainder in a savings bond that earns 7%. If the total interest earned after one year is $420, how much money was invested at each rate?

Step-by-step explanation:

The problem statement is not clear regarding which money is invested. We will assume it is the 80% of $8750 that is set aside for future education. That amount is

... 0.80 × $8750 = $7000

If x represents the amount invested at 7%, then the total interest earned is

... (7000 -x)×4% + (x)×7% = 420

... 280 +0.03x = 420

... x = 140/0.03 ≈ 4666.67

$4666.67 was invested at 7%.

$2333.33 was invested at 4%.

(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

77

step-by-step explanation: