We call:

as the set of <span>the first 51 consecutive odd positive integers, so:
</span>

Where:





<span>and so on.
In mathematics, a sequence of numbers, such that the difference between two consecutive terms is constant, is called Arithmetic Progression, so:
3-1 = 2
5-3 = 2
7-5 = 2
9-7 = 2 and so on.
Then, the common difference is 2, thus:
</span>

<span>
Then:
</span>

<span>
So, we need to find the sum of the members of the finite series, which is called arithmetic series:
There is a formula for arithmetic series, namely:
</span>

<span>
Therefore, we need to find:
</span>
Given that

, then:

Thus:

Lastly:
Answer:
x = 20°
y = 70°
Step-by-step explanation:
the angle adjacent to the 40° angle must be 140° because the two angles form a straight line (which contains 180°)
in the isosceles triangle with the 'x', that means the other two angles must be equal and are (180-140) ÷ 2, which equals 20°
to find 'y', consider the larger right triangle with angles of 90° and 20°; angle y must equal 180 - (90 + 20) = 70°