Question

Variable y varies directly with variable x, and y = 4 when x = 7.

What is the value of x when y = 12?

i think it is 21

Answer 1

so if y=4 =>x=7
y=12 =>x=?

Answer 2

? what do you mean

Answer 3

x/12=7/4

Answer 4

x=7/4*12=7*3=21

Answer 5

yeah

Answer 6

so x=21 when y=12

Answer 7

yes thank you

Answer 8

np

Answer 9

Direct variation is expressed as:
\(y = kx\)
where k is a constant (a number).
Start with the direct variation equation:
\(y = kx\)
Now plug in the given point \((7, 4)\) to find the value of k:
\(4 = k \times 7\)
Which gives \(k = \dfrac{4}{7}\)
Now you plug in the value of k in the direct variation equation:
\(y = \dfrac{4}{7} x\)
The question now is what x value do you have when y = 12?
\(12 = \dfrac{4}{7}x\)
Multiply both sides by 7/4 to get:
x = 21