Solve the system by substitution -4-y=17 and 4y=x

x = -84

y = -21

Step-by-step explanation:

4 - y = 17

4y = x

Use the first equation to solve for y

4 - y = 17

y = 4 -  17

y = -21

In the second equation, get y on its own.

4y = x

y = x/4

Substitute the new second equation into the new first equation

-21 = x/4

-21 * 4 = x

x = -84

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