В учебнике в первом примере опечатка, скорее всего он должен выглядеть так:
$(70 \overset{1}{-} 26) \overset{2}{:} 4 \overset{6}{+} 3 \overset{3}{*} 15 \overset{7}{-} 7 \overset{4}{*} 8 \overset{5}{:} 2 = 44 : 4 + 45 - 56 : 2 = 11 + 45 - 28 = 56 - 28 = 28$
1) 70 − 26 = 44;
2) 44 : 4 = (40 + 4) : 4 = 40 : 4 + 4 : 4 = 10 + 1 = 11;
3) 3 * 15 = (10 + 5) * 3 = 10 * 3 + 5 * 3 = 30 + 15 = 45;
4) 7 * 8 = 56;
5) 56 : 2 = (40 + 16) : 2 = 40 : 2 + 16 : 2 = 20 + 8 = 28;
6) 11 + 45 = 56;
7) 56 − 28 = 28.
 
$400 \overset{5}{:} 50 \overset{6}{*} 9 \overset{9}{-} 3 \overset{7}{*} (20 \overset{1}{:} 5 \overset{3}{+} 35 \overset{2}{:} 7) \overset{45}{+} 480 \overset{8}{:} (6 \overset{4}{*} 8) = 8 * 9 - 3 * (4 + 5) + 480 : 48 = 72 - 3 * 9 + 10 = 72 - 27 + 10 = 45 + 10 = 55$
1) 20 : 5 = 4;
2) 35 : 7 = 5;
3) 4 + 5 = 9;
4) 6 * 8 = 48;
5) 400 : 50 = 40 : 5 = 8;
6) 8 * 9 = 72;
7) 3 * 9 = 27;
8) 480 : 48 = 10;
9) 72 − 27 = 45;
10) 45 + 10 = 55.