PLEASE HELP WILL MARK AS BRAINLIEST

Since there is alot here I will answer a few so that you can apply the same logic to the others

Substitute the values into each equation and simplify

19. 4xy

X = 1 and Y = 3

4 * 1 * 3 = 12

25. 4yz - 8xy

X = 1, Y = 3 and Z = 4

4 * 3 * 4  -  8 * 1 * 3

48 - 24 = 24

31. 3p(2q + r)

p = 2, q = 1 and r = 3

3 * 2 (2 * 1 + 3)

6 (2 + 3)

12 + 18 = 30

38. 3qr + p(2q + r)

p = 2, q = 1 and r = 3

3 * 1 * 3 + 2(2 * 1 + 3)

9 + 2(2 + 3)

9 + 4 + 6 = 19

Feel free to comment if you need more explanation

it has to have an angle of 90 degrees