<PRE><B>Question 947327</B>
d=dimes; q=quarters
d+q=30 solve for d, subtract q from each side
d=30-q
$0.10d+$0.25q=$5.70 

METHOD 1:
Substitute for d
$0.10(30-q)+$0.25q=$5.70
$3.00-$0.10q+$0.25q=$5.70 Subtract $3.00 from each side
$0.15q=$2.70 Divide each side by $0.15
q=18  ANSWER 1 There are 18 quarters.
d=30-q=30-18=12 ANSWER 2 There are 12 dimes.
CHECK 
$0.10(12)+$0.25(18)=$5.70
$1.20+$4.50=$5.70
$5.70=$5.70

METHOD 2:
d+q=30 Multiply this by $0.10 and subtract from equation below
$0.10d+$0.25q=$5.70
$0.10d+$0.10q=$3.00
____________________
       $0.15q=$2.70
Results same as above</PRE>