Given gradient (-2/3) y intercept (3)

Question Use the gradient to find the y coordinate on the line were

x=6

my working out

y^{2}-y^{1}/x^{2}-x^{1}

y-0/0-6 = 2/3 (Negative)

y/-6=2/3(Negative)

y=(negative) 2/3 x (negative) 6/1

y=12/3

y=4

I know the answer is supposed to be negative but I don't know where I went wrong.

Also the answer is negative 1.