Slope = - 1, y-intercept = 6

y=mx+c

where m is the slope/gradient and c is the y-intercept,

so with the values given we get the equation

y = - 1x+6

to find the x intercept y=0

0 = - 1*x+6

-6=-1*x

-6/-1 = x

6=x

and to confirm the y-intercept ... x=0

y = - 1*0+6

y = 6