Shari and Ana are playing games at an arcade. Shari has $37.50 and is playing $0.50 games. Ana has $42.75 and is playing $0.75 games. Sandor wants to know when Shari and Ana will have the same amount of money remaining. So he wrote and solved this equation.

Let x = number of games played.

Equation: 37.50 – .5x = 42.75 – .75x

Step 1: 37.50 – 1.25x = 42.75

Step 2: – 1.25x = 5.25

Step 3: – 4.2 = x

Sandor knows his answer is incorrect because a negative number of games cannot be played. What was Sandor’s mistake?