Answer :
Make a system of equations:
0.10x + 0.25y = 3.95
x + y = 23
x + y = 23
Subtract 'y' to both sides:
x = -y + 23
Plug in -y + 23 for 'x' in the first equation:
0.10(-y + 23) + 0.25y = 3.95
Distribute 0.10:
-0.10y + 2.3 + 0.25y = 3.95
Subtract 2.3 to both sides:
-0.10y + 0.25y = 1.65
Combine like terms:
0.15y = 1.65
Divide 0.15 to both sides:
y = 11
Plug this into any of the two equations to find 'x':
x + y = 23
x + 11 = 23
Subtract 11 to both sides:
x = 12
So Sally has 11 dimes and 12 quarters.
0.10x + 0.25y = 3.95
x + y = 23
x + y = 23
Subtract 'y' to both sides:
x = -y + 23
Plug in -y + 23 for 'x' in the first equation:
0.10(-y + 23) + 0.25y = 3.95
Distribute 0.10:
-0.10y + 2.3 + 0.25y = 3.95
Subtract 2.3 to both sides:
-0.10y + 0.25y = 1.65
Combine like terms:
0.15y = 1.65
Divide 0.15 to both sides:
y = 11
Plug this into any of the two equations to find 'x':
x + y = 23
x + 11 = 23
Subtract 11 to both sides:
x = 12
So Sally has 11 dimes and 12 quarters.
