[(a+3)x3+3]x3+3=102
b+3 =102
b=99
[(a+3)x3+3]x3=99
cx3=99
c=99/3=33
(a+3)x3+3=33
d+3=33
d=30
(a+3)x3=30
a+3=30/3=10
a+3=10
a=10-3
a=7
5x a:3=2525
5xa =2525x3
5xa=7575
a=1515
[ ( a + 3 ) x 3 + 3 ] x 3 + 3 = 102
[ ( a + 3 ) x 3 + 3 ] x 3 = 102 - 3
[ ( a + 3 ) x 3 + 3 ] x 3 = 99
( a + 3 ) x 3 + 3 = 99 : 3
( a + 3 ) x 3 + 3 = 33
( a + 3 ) x 3 = 33 - 3
a + 3 = 30 : 3
a + 3 = 10
a = 10 - 3
a = 7 → numarul necunoscut
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5 x a : 3 = 2 525
5 x a = 2 525 x 3
5 x a = 7 575
a = 7 575 : 5
a = 1 515
