Answer :
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
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