Applying Descartes' Sign rule on the equation $f(x)$= $x^7 + 2x^5 + 3x^3 + 4x - 2018=0$
The number of sign changes in $f(x)$ = number of positive real roots = 1
$f(-x)$= $-x^7 - 2x^5 - 3x^3 - 4x - 2018=0$
Number of sign changes in $f(-x)$ = number of negative real roots = 0
Hence number of real roots of the equation = 1