1)
a + 2a = 18,54
3a = 18,54
a = 18,54 : 3
a = 6,18 - numarul
2)
(6,2 + a) :2 = 9,5
6,2 + a = 9,5 x 2
6,2 + a = 19
a = 19 - 6,2
a = 12,8 - numarul
3)
a+b = 182,5
a -b = 18,17
a = 18,17+b
18,17 +b +b = 182,5
18,17 +2b = 182,5
2b = 182,5 - 18,17
2b = 164,33
b = 164,33 : 2
b= 82,165
a = 82,165 + 18,17 = 100,335
4)
x - 5,2 <7
x < 7+5,2
x < 12,2
x ={ 0,1,2,3,4,5,6,7,8,9,10,11,12}
x + 9,5 <=10,5
x < = 10,5 - 9,5
x < = 1
x = {-inf... 0,1}