a) 10+10:{[10+10x(a-10)]:10-10}=11
10:{[10+10x(a-10)]:10-10} = 11
[10+10x(a-10)]:10-10 = 10
[10+10x(a-10)]:10 = 20
10+10x(a-10) = 200
10x(a-10) = 190
a-10 = 19
a = 29
b) [(a:2-864:8)x5+25x14]:10=52
(a:2-108)x5+350 = 520
(a:2 - 108) x 5 = 170
a:2 - 108 = 34
a:2 = 142
a = 284