Answer:
y = 9
Step-by-step explanation:
So if x = 3, we can sub that into the equation.
This gives us:
6.4 (* 3) + 2.8y = 44.4
so:
19.2 + 2.8y = 44.4
25.2 = 2.8y
so
y = 9
Not possible, you know you have to have at least 5 nickels so substract those first, now your at 4.50. you cant get to 54 coins after that
The equation of a circle:

(h,k) - the coordinates of the centre
r - the radius
Here is the formula that your going to need to use A=P(1+r/n)^nt
So P=500, R=0.082, N=1, T=15
Plug it into your equation and you have A=500(1+0.082/1)^(1)(15)
Simplify what's in the parenthesis A=500(1.082)^(1)(15)
Multiply your exponents A=500(1.082)^15 Then A=500(3.26)
Finally you multiply your last two numbers to get A=1,630
So after 15 years you would have $1,630
I hope this helped you :)