Posted by **HELPP!!!** on Thursday, January 10, 2013 at 10:07pm.

If y varies directly as x and y=3 when x=10, find x when y=8? Can you please show me step by step solution for this problem?

- Math -
**Reiny**, Thursday, January 10, 2013 at 10:55pm
Whenever you have a statement such like yours,

"If y varies directly as x "

you can form the equation

y = kx , where k is a constant

sub in the given: y=3 , x=10 to find k

3 = k(10)

k = 3/10

so your equation is y = (3/10)x

then when y = 8

8 = (3/10)x

80 = 3x

x = 80/3

btw, if it has said" y varies inversely as x" your equation would have been

y = k(1/x), but you would follow the same steps of subbing in the given data to find k

- Math -
**HELPP!!!**, Thursday, January 10, 2013 at 11:03pm
Thank you so much that helps a lot!

- Math -
**Reiny**, Thursday, January 10, 2013 at 11:05pm
welcome

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