I will do (a) only.
6rt - 3st + 6ru - 3su
6rt - 3st = 3t(2r - s)
6ru - 3su = 3u(2r - s)
Answer: (3t + 3u)(2r - s)
Do the rest likewise.
I assume you're asking where it meets the y axis
In an equation the last number is the y intercept so I'm this case it would be 1