`283.56+142.04+661.78=?`

What value will come in place of question mark (?) in the questions given below? 13.4 x 14.2 - 7.4 x 7.8 = ?

22:33:142:n

283xx56+252=20 xx ?

What must be added to the given numbers so that they are in proportion? a. 1, 3, 10, 18 b. 23, 34, 56, 78

142. 49: 216 : : 36 : ?

950 661 436 269 146 65 16