40 * 7 =4 * 10 * 7 = ( 4 * 7 ) * 10 =280
80 * 6 = 8 * 10 * 6 = ( 8 * 6) * 10 = 48 * 10 = 480
9 * 50 = 9 * 5 * 10 = ( 9 * 5) * 10 = 45 * 10 = 450
6 * 70 = 6 * 7 * 10 = ( 6 * 7) * 10 = 42 * 10=420
50 * 70 =5 * 10 * 7 * 10 = ( 5 * 7) * ( 10 * 10) = 35 * 100 = 3500
90 * 60 = 9 *10 * 6 * 10 = ( 9 * 6) * ( 10 * 10) = 54 * 100 = 5400
60 * 30 = 6 * 10 * 3 * 10 = ( 6 * 3) * ( 10 * 10) = 18 * 100 = 1800
30 * 90 = 3 * 10 * 9 * 10 = ( 3 * 9) * (10 *10 ) = 27 * 100 = 2700
40 * 50 + 30 * 8 = 4 * 10 * 5 * 10 + 3 * 10 * 8 =( 4 * 5) * ( 10 * 10) + (3 * 8) * 10 =
= 20 * 100 + 24 * 10 = 2000 + 240 = 2 240
x*0,16 = 2/3*192
0,16x = 128
x = 800