27.
521 = 10 - 0 + n
521 = 10 + n
-n = 10-521
-n = -511
n = 511
28.
4+ ( 4- 4 + a) ÷ 4 =8
4+ a ÷ 4= 8
4 + 1/4 a = 8
16 + a = 32
a = 32 -16
a= 16
29.
1/6 b × 2 ×3 = 8+8 + 1 +13
1/3 b × 3= 30
b = 30
30.
113 + 904= 2000 -y + y ÷ y , y≠0
1017 = 2000 -y + 1
1017 = 2001 - y
y = 2001 - 1017
y = 984 , y≠0
y = 984
31.
( 1/5 h - 5) × 9 + 31= 40
9/5 h -45 +31= 40
9/5 h - 14 = 40
9h - 70 = 200
9h = 270
h= 30
32.
u ≠ 0
8+6 ( 4+27 ÷ (9u)) = 49 + 1
8+6(4 + 27/(9u)) = 50
8 +6 (4+ 3/u) = 50
8+ 24 + 18/u = 50
32 + 18/u = 50
18/u = 50-32
18/u = 18
18 = 18u
1 = u
u=1 , u≠0
u=1
33.
(12-3 +3÷3) z +1 = 41
(12-3+1 ) z+1 = 41
10z + 1 = 41
10z = 41 -1
10z = 40
z = 4
34.
6× 9 - o +10 = 29-1
54 - o + 10 = 28
64 - o = 28
-o = 28 - 64
- o = - 36
o = 36
35.
33 ÷ ( r + 19 ) = 1
33 / ( r+19) = 1
33 = r +19
r = 14
.......
