Question

Solve:$2<3x+7$ when $x$ is an natural number

Answer 1

$2<3x+7$

$\Rightarrow 2<3x+7$

$\Rightarrow 3x+7<2$

$\Rightarrow 3x+7-7<2-7$

$\Rightarrow 3x<-5$

$\Rightarrow x<\frac{-5}{3}$

$\therefore x\in \varphi$