.

Once you have solved for y, gradient = coefficient of x.

Parallel lines have the same gradient.

The product of the gradients of a pair of perpendicular lines is equal to -1.

Without further data, the best you can do is express the equation of each required line in the form y = mx + c where m is the gradient (which you can calculate) and c is the y-intercept (for which there is not enough data to get a value of).