Knew u were going to send that pic
Read that carefully. It doesn't say that nahco3 is insoluble in water anywhere. In solvay process, the soln is slightly basic due to addition of ammonia so nahco3 precipitates and nh4cl doesn't.
In the question, we are concerned with solubility of nahco3 is pure aqueous medium and in fact nahco3 is 'very' soluble in water.