Calculate drill

Thank you for playing. 1,000 downloaded!! One character of a formula becomes a blank. The position of a blank is never the same. Mode 1. 1 digit and 1 digit calculate. Selection from among the four. 2. 1 digit and 1 digit calculate. Direct input. 3. 2 digit and 2 digit calculate. Selection from among the four. 4. 2 digit and 2 digit calculate. Direct input. 2 digit calculate is difficult. Do you answer correctly?