You substitute in an expression by filling in the desired and accustomed unknown value to the value you're trying to find. An example below can better elaborate what I want to say above. In the equation below, 7 - 2n = 5 the unknown is represented by n moreover, the equation suggest to find the missing to make it equilateral on both sides.
In mathematical expression, the equation then becomes 7 - 2n = 5
The next procedure is to find the unknown.
1. 7 - 2n = 5
2. -2n = 5 - 7
3. -2n = -2
4. n = -2/-2
5. n = 1
Check:
Substitute n = 1
7 - 2 (1) = 5
7-2 = 5
5=5
Answer:
i
Step-by-step explanation:
Now, before you think I'm just stealing points, let me explain. The square root of a number is the number that, if you multiply it by itself, it equals that number. The square root of 4 is 2, because 2 * 2 = 4.
Also, a negative number times another negative number, is a positive number. -2 * -2 = 4
With both of those true, then what number could be multiplied by itself to equal a negative number? i.
i is a weird number that I don't really know how to explain all that well. I am sorry, but that is all that I can give you. i is very complex and has various different equivalents, and different meanings, but i is equal to 
.
Hope that this helps!
21. In a parallelogram, opposite angles are equal and adjacent angles are supplementary (add to 180°).
m∠R = m∠P = 180° -m∠Q
m∠Q = 107°
m∠P = 73°
25. If you draw any diagonal, it divides the figure into two congruent triangles (by the SSS postulate). Corresponding angles are congruent, so the diagonal is a transversal between parallel lines. Thus opposite sides are parallel and the figure is a parallelogram.
27. Opposite sides are equal, and the diagonals bisect each other. Your four equations are
2w+4 = 5w-6 . . . . w = 10/3
12 = 3x-3 . . . . . . . x = 5
6y = 4y+6 . . . . . . . y = 3
27 = (5/4)z +2 . . . z = 20
46.5cm squared I believe
Hope this helped ;)
