Answer:
-38x+35
Step-by-step explanation:
Like terms are added :
-10x + 14 (-28x)+21 =
-10x +(-28x) is the same thing as -10x-28x, which equals -38x. Then, 21+14 is 35. So, you're simplest answer of this expression is -38x+35, by adding the like terms. If one of the "x" was squared then, you couldn't add them.