The variable y is directly proportional to the variable x. If y = 21 when x = 9, what is the value of y when x = 12?.

28

Step-by-step explanation:

So we can represent the x-y relationship with a fraction, 21/9(y/x)

Let’s take the unknown y number as “y”

So y/12=21/9(since they are proportional they equal each other)

1)cross multiply:

9y=12*21

9y=252

Divide both sides by 9

Y=28

Hope this helps!

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step-by-step explanation:

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step by step resolutions

1) n+n+1+n+2=51

3n+3=51

3n=48

n=16

the three numbers are 16, 17 and 18.

2) x+15=4x

3x=15

x=5

radha is now 5 years old

3) the two digits are x and y.

y=3x

(10x+y)+(10y+x)=88

y=3x

11x+11y=88

y=3x

x+y=8

x+3x=8

x=2

the original number can be either 28 or 82.

4) n+(n+2)+(n+4)=48

3n+6=48

3n=42

n=14

the numbers are 14, 16 and 18.

5) y=x+3

10y+x+10x+y=143

y=x+3

11x+11y=143

y=x+3

x+y=13

x+x+3=13

2x=10

x=5

the original number can be 57 or 75.

hope this !