If y varies directly with x, if y=12 when x=18, how do you find x when y=-16?

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Answer 1 · 2016-01-01T16:59:50

#color(blue)(x=-24# , when y =-16

#y# varies directly with #x# this implies that as #x# increases #y# increases too.

Let us introduce constant of proportionality #color(blue)(k#

#y=color(blue)(k)x#

#color(blue)(k)=y/x#

We have been provided with values for #x# and #y#
#color(blue)(k)=12/18#

#k=2/3# , this value stays constant.

So when #y=-16#

#x=y/k#

#x=-16/(2/3)#

#x=(-16 xx 3)/2#

#x=(-48)/2#

#color(blue)(x=-24#