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

Add:

(i) 3mn, -5mn, 8mn -4mn

(ii) t - 8tz, 3tz – z, z - t

(iii) -7mn + 5, 12mn + 2, 9mn – 8, -2mn -3

(iv) a + b -3, b - a + 3, a - b + 3

(v) 14x + 10y - 12xy – 13, 18 - 7x - 10y + 8xy,4xy

(vi) 5m - 7n, 3n - 4m + 2, 2m - 3mn -5

(vii) 4x²y, -3xy², -5xy², 5x²y

(viii) 3p²q² - 4pq + 5, -10p²q², 15 + 9pq + 7p²q²

(ix) ab - 4a, 4b – ab, 4a - 4b

(x) x² - y² – 1, y² - 1 - x², 1 - x² - y²

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

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