#### Answer

$-10$

#### Work Step by Step

Subtract $3x$ on both sides of the equation to obtain:
$2x+20=0$
Subtract $20$ on both sides of the equation to obtain:
$2x=-20$
Divide by 2 on both sides of the equation to obtain:
$x = \frac{-20}{2}
\\x=-10$
Check:
$5(-10)+20 =3(-10)
\\-50+20=-30
\\-30=-30$