Nukber of subsets of [n] have that contain exactly one of the elements 1 and 2?

We assume your [n] means the set {1, 2, 3, ..., n}.

For a subset with n elements, there are 2^n subsets. If we remove 1 and 2 from consideration, then your set [n] contains n-2 elements, hence has 2^(n-2) subsets.

There are two ways to have exactly one of the elements 1 or 2: add {1} to the subsets just described, or add {2} to the subsets just described. Thus, ...

... the number of subsets of [n] that contain exactly one of 1 or 2 will be 2^(n-1).

Example: n=3

There will be 2^(3-1) = 4 subsets containing one of 1 or 2:

... {1}, {2}, {1, 3}, {2, 3}

wholesale price is the initial price before markup. retail price comes after the markup.

a price of 8 bucks that's marked up by 100%   is

formula: initial price + (percent markup in fraction/decimal)(initial price)

8+(1)(8)

8+8

16

retail price is $16.

the sum of the lengths of any two sides of a triangle is greater than the length of the third side. if you take the three sides of a triangle and add them in pairs, the sum is greater than (not equal to) the third side. if that is not true, then it is not possible to construct a triangle with the given side lengths.

step-by-step explanation: