Acollege student and $72,000 during summer vacation working as a waiter in the restaurant on the boardwalk at the beach. the student invested part of the money at 10% and the rest at 9%. if the student received a total of $680 in interest at the end of the year, how much was invested at 10%?

$3,200

Step-by-step explanation:

The information "72,000" should be "7200".

Basically the question is

"7200 invested in 2 accounts, 10% and 9% interest accounts. After 1 year, interest earned is 680. So much was invested in 10% account??"

let amount invested in 10% be x

let amount invested in 9% be y

The formula is:

Where

SI is simple interest

P is the amount invested

r is the rate of interest (in decimal. percentage divided by 100 is decimal)

t is the time [here, t = 1, since after 1 year]

So, the equation can be written as:

x(0.10)(1) + y(0.09)(1) = 680

Also, y = 7200 - x

Substituting we get:

x(0.10) + (7200 - x)(0.09) = 680

Now we can solve for x:

Thus, $3,200 was invested in 10%

infinitely many solutions

step-by-step explanation:

we have been given the equation;

2(2x + 3) = -4 + 2(2x + 5)

we need to determine the value of x.

2(2x + 3), we expand this expression to obtain 4x + 6

similarly 2(2x + 5) will become 4x + 10

now we have;

4x + 6 = -4 + 4x + 10

4x + 6 = 4x + 10 - 4

4x + 6 = 4x + 6

the expression on the left hand side is identical to the one on the right hand side. therefore, we are looking at just a single straight line whose equation is;

y = 4x + 6

consequently, we shall have infinitely many solutions