If x / 7 = 9 / y, then what's the ratio between X and y? Why?

If x / 7 = 9 / y, then what's the ratio between X and y? Why?

If x / 7 = 9 / y, then x and y are inversely proportional
Because: X / 7 = 9 / y, then xy = 7 × 9
That is: xy = 63 (certain), so x and y are inversely proportional

What's the ratio of x = 9 / 7, X and Y. y = x + 7, X and y? Why?

X / 7 = 9 / y, X and YX / 7 = 9 / y, xy = 7 * 9, xy = 63 (the product is certain), so XY is inversely proportional. Y = x + 7, X and YXY are not proportional. Because the product of XY is not a fixed value, the ratio is not a fixed value, so it is not proportional. The key to judge whether two quantities are proportional is to see whether the ratio of these two quantities is fixed, or whether the product is certain

If y of 8 = 9 of X, what's the ratio of X to y? Why?

Inverse proportion
because
x=9/(y/8)=72/y
xy=72
Because 72 is certain, a big is B small, a small is B big