Answer
x=7
Work Step by Step
The single arcs on the diagram show that $\angle BDK\cong\angle JDR$ so
$3x+4=5x-10$
subtract 3x from each side
$3x+4-3x=5x-10-3x$
combine like terms
$4=2x-10$
add 10 to each side
$4+10=2x-10+10$
$14=2x$
divide each side by 2
$14\div2=2x\div2$
$7=x$