Answer:

Complete Solution:

A smile is worth $15. A frown is worth $10, and a neutral face is worth $12.

There are many ways to approach this challenge.

• Top row (2 smiles and 1 frown) = $40

• Middle column (2 smiles and 2 frowns) = $50

The middle column has one more frown and costs $10 more than the top row, so:

• 1 frown = $10

• Since 2 smiles and 1 frown = $40 and 1 frown = $10,

• Subtracting 2 smiles = $30, so that

• 1 smile = $15

Alternate Solution:

Another way is to use the first and third rows:

• Top row (2 smiles and 1 frown) = $40

• Third row (1 smile and 2 frowns) = $35

Continue the pattern, lose a smile, and add a frown for $5 less:

• 0 smiles and 3 frowns = $30

• 1 frown = $10

Then continue the first method to find the cost of a smile.