[1] If X Class A vehicles are rented, (8-x) Class B vehicles are rented.

therefore

40x+30(8-x)>=290

10x+20 (8-x)>= 100

Then find x and you can get the result.

[2] Y=2000x+ 1800(8-x)

Simplify, according to the first question, you can get the result.