1. B si c ajutor va rog

b)

(3*x-11):2+18=20

(3*x-11):2=20-18

(3*x-11):2=2

3*x-11=2*2

3*x-11=4

3*x=4+11

3*x=15

x=15:3

x=5

c)

2*x+4≤10

2*x≤10-4

2*x≤6

x≤6:2

x≤3

x∈N => x∈{0,1,2,3}

[tex] \it a)\ (3\cdot x-11):2 +18 =20|_{-18} \Rightarrow (3\cdot x-11):2 =2|_{\cdot2} \Rightarrow \\ \\ \Rightarrow 3\cdot x-11 =4 |_{+11} \Rightarrow 3\cdot x=15 \Rightarrow x = 5\\ \\ \\\ 2\cdot x+4\leq10|_{-4} \Rightarrow 2\cdot x\leq6 \Rightarrow x\in\{0,\ \ 1,\ \ 2,\ \ 3\} [/tex]