$5000 is invested into two accounts. One pays 5% interest and the other pays 7%. The total investment earned $310 interest. Write the system of equations that describes this situation
and then solve the system to determine how much was invested at 5% interest and how
much was invested at 7% interest.

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116

step-by-step explanation:

i think its about 8

the exponential expression to find the value of the cd, in dollars, after t years will be:  

step-by-step explanation:

formula of compound interest:   , where final value after years,   initial value, rate of interest in decimal and number of compounding in a year.

oliver plans to purchase a $1,500 certificate of deposit (cd) at his bank. that means,  

the cd will earn 2.3% interest, compounded semi-annually.

so,   and  

now, plugging these values into the above formula, we will

(rounded to the nearest ten-thousandth)

so, the exponential expression to find the value of the cd, in dollars, after t years will be: