Slope intercept form is:
y = mx + b
"m" is the slope, "b" is your y-intercept (where x = 0)
Since you know m = 12, you can plug it into the equation
y = 12x + b
To find "b", you plug in the point (0 , 2/3) into the equation.
y = 12x + b
2/3 = 12(0) + b
2/3 = b
Now that you know "b", you can plug it in. Your equation is:
y = 12x + 2/3