So, if you're trying to solve an equation, here's an example:
2x + 4y = 8
You would minus 2x from both sides. (you want to get the equation into a mx + b format)
4y= -2x + 8
you would now divide both sides by 4
y = -1/2x + 2
So now that your equation is in y = mx+b, you should know your answer.
mx= to slope
b= y-intercept
so, therefore, your y-intercept is 2.