This paragraph b=(6-a)/(a-3)

∴y= 1/(a-3)x+(6-a)/(a-3)

The calculation is wrong.

b=-a/(a-3)

∴y= 1/(a-3)x-a/(a-3)

Substituting y=2 gives x=3a-6.

① when s (bpqc): s (adqp) = 1: 3.

(3a-6+a- 1)* 1/2 = 1/4 *(5+3)* 1/2

4a-7=2

a=9/4

∴P( 1)(9/4,0)

There's another one, too. It took a lot of effort. Here you are.