810 − 70 + 160 = 900
640 : 10 : 4 = 16
15 * 6 + 830 = 920
560 : 8 + 90 = 160
8 * 12 + 504 = 600
96 : 24 * 17 = 68

Вычисления:
$810 \overset{1}{-} 70 \overset{2}{+} 160 = 900$
1) 810 − 70 = 740
2) 740 + 160 = 900
 
$640 \overset{1}{:} 10 \overset{2}{:} 4 = 16$
1) 640 : 10 = 64
2) 64 : 4 = (40 + 24) : 4 = 40 : 4 + 24 : 4 = 10 + 6 = 16
 
$15 \overset{1}{*} 6 \overset{2}{+} 830 = 920$
1) 15 * 6 = (10 + 5) * 6 = 10 * 6 + 5 * 6 = 60 + 30 = 90
2) 90 + 830 = 920
 
$560 \overset{1}{:} 8 \overset{2}{+} 90 = 160$
1) 560 : 8 = 70
2) 70 + 90 = 160
 
$8 \overset{1}{*} 12 \overset{2}{+} 504 = 600$
1) 8 * 12 = 8 * (10 + 2) = 8 * 10 + 8 * 2 = 80 + 16 = 96
2) 96 + 504 = 600
 
$96 \overset{1}{:} 24 \overset{2}{*} 17 = 68$
1) 96 : 24 = 4
2) 4 * 17 = 4 * (10 + 7) = 4 * 10 + 4 * 7 = 40 + 28 = 68