Soro bought a $50.00 bus card at the beginning of the week. Each bus ride costs $2.50. He needs to have at least $20.00 on his card at the end of this month. To determine how many bus rides he can take between now and the end of this month, Soro wrote and solved the following inequality: 50 minus 2.5 x greater-than-or-equal-to 20. Negative 2.5 x greater-than-or-equal-to negative 30. x greater-than-or-equal-to 12.

What error, if any, did Soro make when writing or solving this inequality?