what you do is you add the like terms. so everything that has the same coefficient (the letter attached to the number) is a like term
so you add the numbers for each like term together because you have a + in between the polynomials
so -x2 (im guessing this is x squared?) and -3x2 are like terms. if you add the numbers, thats -1 and -3 (if there's not a number attached to the term it's just a 1) which is -4 and if you attach that back to the like term it's -4x2
-11x doesn't have a like term so you keep it how it is
9 and 4 are like terms, if you add them you get 13
all together, that's -4x2 -11x +13
if that still doesn't make sense, tell me and i'll try to help more!!