Which expression cannot be simplified?

a. 8x - 8
b. 8x - x
c. 8x + 5x
d. (8 + 5)x
e. -(x + x)

i think it's c because it is the simplified version of d. (8 + 5)x, but i could be wrong and i need to show my work for the others, which i don't quite understand how i could simplify 8x - 8 as it is pretty simple already.

Abag contains 4 red, 7 blue and 5 yellow marbles. event a is defined as drawing a yellow marble on the first draw and event b is defined as drawing a blue marble on the second draw. if two marbles are drawn from the bag, one after the other and not replaced, what is p(b|a) expressed in simplest form? a. 7/16 b. 7/15 c. 14/16 d. 14/15

Find the ratios of the corresponding sides

There are 10 chicks on ginger's farm .she has 2 chicks in one outdoor pen and 5 chicks in another. the rest of the chicks are in the barn.what is the fraction of total chicks in outdoor pens?