Answer
$x=10.5$
Work Step by Step
$(-8)^2+3x=5x+43$ $\longrightarrow$resolve exponent
$64+3x=5x+43$ $\longrightarrow$addition property
$64+3x-3x-43=5x+43-3x-43$ $\longrightarrow$simplify
$21=2x$ $\longrightarrow$multiplication property
$21\div2=2x\div2$ $\longrightarrow$simplify
$10.5=x$