Solve for a
a=-\frac{b}{4}+\frac{9}{2}
Solve for b
b=18-4a
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4a=18-b
Subtract b from both sides.
\frac{4a}{4}=\frac{18-b}{4}
Divide both sides by 4.
a=\frac{18-b}{4}
Dividing by 4 undoes the multiplication by 4.
a=-\frac{b}{4}+\frac{9}{2}
Divide 18-b by 4.
b=18-4a
Subtract 4a from both sides.
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