Answer:
a) y*x = k
b) y = 3
Explanation:
a) According to given condition:
As in inverse relation, if one quantity increases other decreases proportionally so the equation will be:
y∝ 1/x
Now removing proportional sign with equality a constant k is used as follows:
y = k/x
k = y*x
Putting values of y and x, we get:
k = (7) * (9)=63
b) By putting given value of x in (k=y*x)
63 = y * (21)
y = 63/21
y = 3