Answer: 
pounds
Step-by-step explanation:
Let x pounds of $ 0.66 per lb candies mixed with y pounds of $ 1.31 per lb candies to obtain 9 lb of $ 0.97 per lb candies,
Hence, we can write,
x + y = 9 ------- (1)
And, 0.66 of x + 1.31 of y = 0.97 of (x + y)
⇒ 66 x + 131 y = 97 (x+y)
⇒ 66 x +131 y - 97 x - 97 y = 0
⇒ -31 x + 34 y = 0 ------(2)
By solving equation (1) and (2)
We get,
and 
Hence, the quantity of 0.66 per lb candies = pounds
The sequence is an arithmetic sequence with
a₁ = -4
d = a₂ - a₁
d = -1 - (-4)
d = -1 + 4
d = 3
an = x
Sn = 437
General formula in arithmetic sequence
Formula to find nth term
an = a₁ + d(n - 1)
Formula to find sum of sequence (sn)
Sn = n/2 (a₁ + an)
We have to make an equation system based on the problem
plug the numbers into the formula
First equation
an = a₁ + d(n - 1)
x = -4 + 3(n - 1)
x = -4 + 3n - 3
x = 3n - 7
Second equation
Sn = n/2 (a₁ + an)
n/2 (a₁ + an) = 437
n/2 (-4 + x) = 437
n(x - 4) = 874
xn - 4n = 874
Solve the equation system by subtitution method
Subtitute x with 3n - 7 in the second equation
xn - 4n = 874
(3n - 7)n - 4n = 874
3n² - 7n - 4n = 874
3n² - 11n - 874 = 0
(3n + 46)(n - 19) = 0
n = -46/3 or n = 19
Because the number of terms shouldn't be negative, -46/3 isn't required, so the value of n is 19.
Solve for x, back to the first equatin
x = 3n - 7
x = 3(19) - 7
x = 57 - 7
x = 50
The solution is 50
If you divide by 7 on both sides to get rid of t, you get -5!
