Question

In an equation, y varies directly is a x varies. If y =86 when x=20, what is the value of x when y=129?​

Answer 1

Since y varies directly as x varies,  when y is 129, x becomes 30.

First, We write out the expression that y varies directly as x giving us

y ∝ x

Introducing the constant of proportionality, K we have that

y = K x

Now when y is 86 and x=20, The constant becomes

y = K x

Plugging in values and  Solving:

86= K x 20

K=86 / 20

K= 4.3

Now to solve for x  When y is 129,

Using our equation that

• y = K x  
•  K= 4.3

Solving out

y = K x

129 = 4.3 x X

X =129/4.3 = 30

X = 30

See more on variation here: brainly.com/question/25572183