Hey there! 
2x - 18x + 36
COMBINE the LIKE TERMS 
(2x - 18x) + 36
2x - 18x = -16x 
36 = 36 because it doesn’t have any like terms 
= -16x + 36
Answer: -16x + 36 or you could simply say 
4(-4x + 9)
Good luck on your assignment and enjoy your day!
~Amphitrite1040:)