I have two questions that I have trouble solving ...

1)P and Q are the points of intersection of the line,

x/a + y/b = 1 (a > 0, b > 0)

with the x- and y-axes respectively. The distance PQ is 20 and the gradient of the PQ is -3. Find the values of a and b.

2)The sides of parallelogram lie along the lines y = 2x - 4, y = 2x - 13, x + y = 5 and x + y = -4. Find the length of one side, and the perpendicular distance between this and the parallel side. Hence find the area of the parallelogram.

Have spent hours but nothing's working