If the value of y varies directly with x and y=-1 when x=3, find y if x=9

1.If y varies directly with x

Introduce the constant term k

2.y=kx

where k is the constant term

substitute the value of x and y to form the law

-1=3k

k=-1\3

:y=-1\3xis the law

To find the value of y when x is 9

Reinstate the law which is y=-1\3x and substitute the value of x to find y

y=-1\3*9

y=-3

30 units^2

step-by-step explanation:

area is l × w

the length is 3

and the width is 10

3 × 10= 30 units squared

a. is correct