x+8 X+5

__________ _ ___________
X^2-10x+21 x^2-3x-28

Subtract, then reduce if possible

Use brackets and / for division

e.g. I am inclined to guess you meant

(x+8)/(x^2 - 10x+21) - (x+5)/(x^2 - 3x - 28)

confirm please