ALgebra
posted by john .
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?

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.