9514 1404 393
Answer:
9
Step-by-step explanation:
"Varies directly" means the values change by the same factor. Here, we have y increasing from 13 to 39, by a factor of 3.
Since x varies directly as y, it, too, will increase by a factor of 3:
x = 3·3
x = 9
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Alternate solution
"Varies directly" is another way to say the values are proportional. Then the new value of x can be found from ...
x-value/y-value = 3/13 = x/39
Multiplying by 39 gives ...
x = 39(3/13) = 3·3
x = 9
