Math
posted by HELPP!!! .
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?

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 
Thank you so much that helps a lot!

welcome