If x varies directly as y, and x=12 when y=3, find x when y=7

28

Step-by-step explanation:

x=12 and y=3

x=4 and y =1

x=28 and y=7

x equals 1

step-by-step explanation:

f(4)=f(×)

x=1

or

step-by-step explanation:

we need to solve for 'x' the following equation:  

we have that:

⇒

⇒ ⇒

factorizing, we get that:

  ⇒

then, the solutions are: or

nothing extraneous has been found!