1) (2 5/9 - 1 20/21):1 8/49+1 8/9 : 6=5/6
2 5/9 - 1 20/21 = 38/63
38/63 : 1 8/49=14/27
1 8/9 : 6= 17/54
14/27+17/54=5/6
2) (1 17/18 * 1 13/14- 2 5/8 : 1 19/20):(2 25/78- 1 1/26)=1 7/8
1 17/18 * 1 13/14=3 3/4
2 5/8 : 1 19/20=1 9/26
3 3/4-1 9/26=2 21/52
2 25/78- 1 1/26= 1 11/39
2 21/52 : 1 11/39=1 7/8
S(полной) = Sосн+ Sбок = 64+ .132 = 196.
S(бок) = 1/2P* апофему = 46/2 = 23 * 4 = 132
Апофема= 10
Soсн= 8^2 = 64
Ответ: 196.
Х:21/25=15/28
х*25/21=15/28
х=15/28:25/21
х=15/28*21/25
х=3/4*3/5
х=9/20
1)837+x=10989
x=10989-837
x=10152
2)6x+908=4052
6x=4052-908
6x=3144
x=3144:6
x=524