PLEASE HELP ILL GIVE BRAINLIEST

x = 6

Step-by-step explanation:

first find the angle

51 + 72 + x = 180

123 + x = 180

x = 180 - 123

x = 57

so the third angle is 57

now find the value of x in the given expression

8x + 9 = 57

8x = 57 - 9

8x = 48

x = 48/8

x = 6

now check whether the value of x is correct or not by evaluating the value of x in expression

8x + 9 = 57

8(6) + 9 = 57

48 + 9 = 57

57 = 57

so its true

Method 2

51 + 72 + (8x + 9) = 180

123 + 8x + 9 = 180

132 + 8x = 180

8x = 180-132

8x = 48

x = 48/8

x = 6

now again you can check by evaluating the value of x in the above expression

l.jnl.j/n.m,lm,

step-by-step explanation:

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional