Use distributive property: [tex]a(b\pm c)=ab\pm ac[/tex]
[tex]-3(4-a)=6\\\\(-3)(4)+(-3)(-a)=6\\\\-12+3a=6\ \ \ |add\ 12\ to\ both\ sides\\\\3a=18\ \ \ |divide\ both\ sides\ by\ 3\\\\\boxed{a=6}[/tex]
[tex]5(x+6)=45\\\\(5)(x)+(5)(6)=45\\\\5x+30=45\ \ \ \ |subtract\ 30\ from\ both\ sides\\\\5x=15\ \ \ \ |divide\ both\ sides\ by\ 5\\\\\boxed{x=3}[/tex]
