Answer
a=5
Work Step by Step
$3a-6=a+4$ $\longrightarrow$ isolate like terms on each side of equation
$3a-6-a+6=a+4-a+6$ $\longrightarrow$ simplify
$2a=10$ $\longrightarrow$ divide both sides by 2
$2a\div2=10\div2$ $\longrightarrow$ simplify
$a=5$