(04.03 LC Given the following system of equations:
3x + 5y = 30
X + 3y = 10
Which action creates an equivalent system that will eliminate one variable when they are combined?

              multiply second equation by (-3)

new system of equations:

3x + 5y = 30

-3x - 9y = -30

Step-by-step explanation:

x + 3y = 10

multiplied by (-3):

-3x - 9y = -30

combinig:

3x+5y + (-3x-9y) = 3x - 3x + 5y - 9y = -4y

10 + (-30) = -20

so:   -4y = -20

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