The x-intercept is the x-value when y = 0 ---> (x, 0) or the point where the line crosses through the x-axis.
To find the x-intercept, you can substitute/plug in 0 into "y" in the equation:
y = 3x + 18 Plug in 0 into "y" since y = 0, then isolate/get the variable "x" by itself
0 = 3x + 18 Now subtract 18 on both sides
-18 = 3x Divide 3 on both sides to get "x" by itself
-6 = x -6 is the x-intercept