Помогите решить 77,78,79

Question 1

Question 2

77)
$8 \frac{1}{2} - 3 \frac{1}{2} \div (2 \frac{1}{2} + 1 \frac{3}{4} ) \times 2 \frac{3}{7} = \frac{17}{2} - \frac{7}{2} \div ( \frac{5}{2} + \frac{7}{4} ) \times \frac{17}{7} = \frac{17}{2} - \frac{7}{2} \div ( \frac{10}{4} + \frac{7}{4} ) \times \frac{17}{7} = \frac{17}{2} - \frac{7}{2} \div \frac{17}{4} \times \frac{17}{7} = \frac{17}{2} - \frac{7}{2} \times \frac{4}{17} \times \frac{17}{7} = \frac{17}{2} - 2 = \frac{17}{2} - \frac{4}{2} = \frac{13}{2} = 6 \frac{1}{2}$
78)
$9 \frac{2}{7} + 1 \frac{7}{9} \div (2 \frac{2}{5} - 1 \frac{1}{3} ) \times \frac{3}{7} = \frac{65}{7} + \frac{16}{9} \div ( \frac{12}{5} - \frac{4}{3} ) \times \frac{3}{7} = \frac{65}{7} + \frac{16}{9} \div ( \frac{36}{15} - \frac{20}{15} ) \times \frac{3}{7} = \frac{65}{7} + \frac{16}{9} \div \frac{16}{15} \times \frac{3}{7} = \frac{65}{7} + \frac{16}{9} \times \frac{15}{16} \times \frac{3}{7} = \frac{65}{7} + \frac{5}{7} = \frac{70}{7} = 10$
79)
$4 \frac{1}{6} + (2 \frac{3}{4} - 2 \frac{1}{6} ) \div 2 \frac{4}{5} - 1 \frac{3}{8} = \frac{25}{6} + ( \frac{11}{4} - \frac{13}{6} ) \div \frac{14}{5} - \frac{11}{8} = \frac{25}{6} + ( \frac{33}{12} - \frac{26}{12} ) \div \frac{14}{5} - \frac{11}{8} = \frac{25}{6} + \frac{7}{12} \times \frac{5}{14} - \frac{11}{8} = \frac{25}{6} + \frac{5}{24} - \frac{11}{8} = \frac{100}{24} + \frac{5}{24} - \frac{33}{24} = \frac{72}{24} = 3$

Question 3

77. 17/2-7/2:(5/2+7/4)*17/7= 17/2-7/2:17/4*17/7=17/2-7/2*4/17*17/7=17/2-2=13/2=6,5
78. 65/7+16/9:(12/5-4/3)*3/7=65/7+16/9*15/16*3/7=65/7+15/21=210/21=10
79. 25/6+(11/4-13/6):14/5-11/8=26/6+14/24*5/14-11/8=25/6+5/24-11/8=72/24=3