Question

Is this expression x+2x+3 equivalent to the expression 3(x+1)

Answer 1

$x+2x+3=3x+3 \\ 3(x+1)=3 \times x + 3 \times 1 =3x+3 \\ \\ x+2x+3=3(x+1)$

Yes, they are equivalent.

Answer 2

$x+2x+3=3x+3=3(x+1)\Rightarrow \hbox{ YES}$