Question

x+21=35,3; 3x+1<32,02inN

Answer 1

$x+21=35,3 \\ x=35,3-21$
$x=14,3$ ∉ $N$ , $x$ ∈ $Q$
$3x+1\ \textless \ 32,02 \\ 3x\ \textless \ 32,02-1 \\ 3x\ \textless \ 31,02 \\ x\ \textless \ \frac{31,02}{3} \\ x\ \textless \ 10,34$
$x$ ∈ $\left \{ 0;1;2;3;4;5;6;7;8;9;10 \left \}$