The variable y varies directly with x . When x = 4, y = 8. Find y
when x = 9.

Y is 18.

I know this because it was my last year syllabus

Okay so I just learned this too. So basically what you want to do is first plug in the 5 only then after you solve after plugging that in rewrite the equation but plug in the -7. If that makes sense. If it doesnt ask me again in the comments to explain more differently