I guess those 'L' are 't'.
Solve for t in both parametric equations:
Now, you have two expressions for t. The must be equal to each other:
Solve for y in this last equation:
And you've got the slope-intercept form.
Yo could also find from the beginning the slope: it's the quotient of the coefficients of the parameter:
And, then find the intercept by plugging the point (2,4) into the equation: