What should be subtracted from 2a+8b+10 to get -3a+7b+16?

Subtract:

(i) -5y² _– from y²

(ii) 6xyfrom -12xy

(iii) (a - b) from (a + b)

(iv) a(b - 5) from b(5 - a)

(v) -m² + 5mn from 4m² – 3mn + 8

(vi) -x² + 10x – 5 from 5x -10 x²

(vii) 5a² - 7ab + 5b² from 3ab – 2a² -2b²

(viii) 4pq - 5q² - 3p² from 5p² + 3q² - pq

What should be added to x²+xy+y² to obtain 2x²+3xy ?

What should be taken away form 3x² - 4y² + 5xy + 20 to obtain -x² - y² + 6xy + 20?

From the sum of 3x - y + 11 and -y – 11, subtract 3x - y - 11.