3 * d = 18
d = 18 : 3
d = 6
-------------
b * 4 = 28
b = 28 : 4
b = 7
---------------
x : 2 = 18
x = 18 * 2
x = 36
--------------
36 : z = 9
z = 36 : 9
z = 4
---------------
20 - m = 7
m = 20 - 7
m = 13
-------------
n - 6 = 12
n = 12 + 6
n = 18
---------------
5 + l = 11
L = 11 - 5
L = 6
-------------
20 = t + 12
t = 20 - 12
t = 8
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