First we will find the 11th term
an = a1 + (n-1) * d
a11 = 12 + (11 - 1) * 5
a11 = 12 + 10 * 5
a11 = 12 + 50
a11 = 62
now we use the sum formula...
Sn = (n (a1 + an)) / 2
S11 = (11 (12 + 62)) / 2
S11 = (11 (74)) / 2
S11 = 814/2
S11 = 407
X - y = 5
x = y + 5
y = x - 5
since 17 is a prime number and 26 is not a multiple of 17
17/26 is in simplest form
Usually when you do expressions involving subtraction you can do Keep, Change ,Change
That means you keep the sign of the first number and change the other two signs.
It is best you rewrite the expression to addition because a lot of people don't do well with subtracting .
1/2^3 = 1/2 x 1/2 x 1/2 = 1/8
Answer is C
