I dont know how to find x

Simplify both sides:

x
—- = -9
4

now isolate the variable (x):

x= -9 • 4
x= -36

Where m is the slope of the line and b is the y-intercept of the line, or the y-coordinate of the point at which the line crosses the y-axis. to write an equation in slope-intercept form, given a graph of that equation, pick two points on the line and use them to find the slope. this is the value of m in the equation.