Question

Algebra ...........................

Answer 1

see explanation

Explanation:

Given that y is inversely proportional to x then the equation relating them is

y =
`(k)/(x)` ← k is the constant of proportion

(a)

To find k use the condition when y = 7 , x = 9, that is

7 =
`(k)/(9)` ( multiply both sides by 9 )

63 = k

y =
`(63)/(x)` ← equation of proportion

(b)

When x = 21, then

y =
`(63)/(21)` = 3