Answer
G- 3
Work Step by Step
$5d+6-3d=12\longrightarrow$ combine like terms
$2d+6=12\longrightarrow$ subtract 6 from each side
$2d+6-6=12-6\longrightarrow$ subtract
$2d=6\longrightarrow$ divide each side by 2
$2d\div2=6\div2\longrightarrow$ divide
$d=3$