Hi,

In the below question

At which point does the line intersect the x axis.

we would take Y = 0 ( when a line intersects the x axis, its Y coordinate would be 0. whereas the x Coordinate would have a definite value)

Question -

A line has a slope 3/4 and intersects the points (-12, -39).At which point does the line intersect the x axis.

Slope line eq -
y= mx + c ( m slope , c is intercept on y axis when x= 0)

Plug the values of x, y, m to find c

-39 = 3/4 * (-12) + c
c= -30

now , To find the point where the line intersects at x axis , substitute y=0 in the above eq

0=mx +c
x= -c/m = 30/ (3/4) = 40

See X-axis means Y=0
Y-axis means X=0

So for X intercept you should take Y=0.