equations of straight lines

Given two st. lines L1: x+4y-10=0 and L2: 3x-8y+15=0

a.Find the equation of st. line L3 passing through(8,-3) and the intersection
point of L1 and L2

b.L4 is a st. line parallel to L3 and cuts the positive x-axis at A and the
positive y-axis at B. The perimeter od triangleAOB is 12.5units.
i.Find the equation of L4
ii.Find the perpendicular distance between L3 and L4