Answer:
or 
Step-by-step explanation:
we have
Divide the absolute value inequality into two inequalities
<em>First inequality</em> (positive value)

<em>Second inequality</em> (negative value)

Multiply by -1 both sides
Remember that when you multiply or divide both sides of an inequality by a negative number, you must reverse the inequality symbol
so

therefore
The compound inequality that can be used is
or 
First, let's identify some variables:
d = dress price
s = shirt price
d = 3s
12s + d = 450
Because d = 3s, we can substitute the variable:
12s + 3s = 450
15s = 450
s = 30
The shirt costs $30, and the dress $10