`7/8` of `616 xx 12 -: 16+?=17xx19+81+4/3xx?`

If 19xx6=38 32xx12=128 17xx9=51 9xx3=?

19 xx 12 + 19 = 19 xx (12 + _____)

13.5 xx 16.3 xx 12.8 = ?

13.5 xx 16.3 xx 12.8 = ?

Find the unit digit of 3^6 xx 4^7 xx 6^3 xx 7^4 xx 8^2 xx 9^5 .

(17) xx (-12) + (19) xx (-12) = …….

3/7 xx 7/17

Find S_n of the following arithmatical geometric sequence. 3, 7 xx 3 , 11 xx 9 , 15 xx 27 , 19 xx 81 , …..

Simplify: (i) 5/12 xx (-36) , (ii) -17/18 xx 12 , (iii) -5/6 xx 6/5 , (iv) -14 xx 9/28 , (v) -12/5 xx (-15) , (vi) -3/4 by 8/7 , (v) -16/9 by 12/-5 , (vi) 35/(-8) by 12/(-5) (vii) -3/10 by -40/9 , (viii) -32/5 by 15/(-16) , (ix) -8/15 by -25/32