[tex]\huge\boxed{906=2r+6\text{; \$}450}[/tex]
Write this out as an equation first, where [tex]r[/tex] represents Ralph's earnings and [tex]d[/tex] represents Dave's earnings.
[tex]d=2r+6[/tex]
Substitute in the known value.
[tex]\boxed{906=2r+6}[/tex]
Subtract [tex]6[/tex] from both sides.
[tex]900=2r[/tex]
Divide both sides by [tex]2[/tex].
[tex]\boxed{450}=r[/tex]
