She should invest $6491.73.
The equation we use to solve this is in the form

,
where A is the total amount in the account, p is the principal invested, r is the interest rate as a decimal, n is the number of times per year the interest is compounded, and t is the amount of time.
A in our problem is 14000.
p is unknown.
r is 6% = 6/100 = 0.06.
n is 2, since it is compounded semiannually.
t is 13.
Answer:
13) x = 30
14) x = 22.5
15) x = 36
Step-by-step explanation:
13) 4x+2x = 180
6x = 180
x = 30
14) 3x+5x = 180
8x = 180
x = 22.5
15) 2x+3x+2x+3x = 360
10x = 360
x = 36
I’m not sure but you can use a calculator I saw a fantasy one at Walmart with A SCREEN ON IT!??? it’s $100 but it would probably help ALOT