Posted by john on .
sam has $3.50 in dimes and quarters. he has 23 quarters all together. how many of each does he have?
will has $2.40 in dimes and nickels. he has 30 coins all together. how many of each does he have?

ALgebra 
Henry,
1. Your prob. says sam has 23qtrs,but
I'm assuming you meant 23 coins; he can't have 23 qtrs if he only has 3.50.
x dimes, y qtrs,
Eq1: x + y = 23 coins,
0.10x + 0.25y = 3.50,
Multiply both sides by 20:
Eq2: 2x + 5y = 70.
Solve the 2 Eqs:
x + y = 23,
2x + 5y = 70,
Multiply the 1st Eq by 2:
2x 2y = 46,
2x + 5y = 70,
Add the 2 Eqs:
3y = 24,
y = 8 Qtrs.
Substitute 8 for y in EQ1:
X + 8 = 23,
X = 23  8,
X = 15 Dimes.
2. Same procedure as prob. 1.