If y varies directly as x, and y is 18 when x is 5, which expression can be used to find the value of y when x is 11?

y=5/18(11)

y=18/5(11)

y=(18)(5)/11

y=11/(18)(5)

Question

If y varies directly as x, and y is 18 when x is 5, which expression can be used to find the value of y when x is 11?

y=5/18(11)

y=18/5(11)

y=(18)(5)/11

y=11/(18)(5)

anonymous · Answer

If y varies directly as x, then y=kx. 

Since y=4, when x=-2, plug it into the formula above, and you have
y=kx
4=k(-2) 

Solve for k, k=-2 

Now, y = -2x, so if x=30

anonymous · Answer

find the equation and get your answer