Answer
$n=-2$
Work Step by Step
$3+2n=4n+7$ $\longrightarrow$addition property of equality
$3+2n-2n-7=4n+7-2n-7$ $\longrightarrow$combine like terms
$-4=2n$ $\longrightarrow$multiplication property of equality
$-4\div2=2n\div2$ $\longrightarrow$simplify
$-2=n$
