Answer
14
Work Step by Step
$5(n+4)=90$
$5(14+4)\overset?=90$
$5(18)\overset?=90$
$90\overset?=90\checkmark$
$5(16+4)\overset?=90$
$5(20)\overset?=90$
$100\overset?=90\ X$
$5(26+4)\overset?=90$
$5(30)\overset?=90$
$150\overset?=90\ X$