Let the linear equation be:

Y=KX+B

Substitute (0, -2) into this formula. b =-2；

So, Y=KX-2

So, the intersection of the image and the x axis is:

0=KX-2，KX=2

(K/2，0)

Y axis coordinates are:

(0,-2)

And K/2*|-2|=3.

So, K=6.

That is, the original linear expression should be: Y=6X-2.