No problem
% m/m = (mass of solute/ mass of solution) * 100%.
A 12% m/m KHCO3 solution means for every 100 g of solution, you have 12 g KHCO3. So for 148 g solution, you need 12%*148g of solution/100% = 17.76 g of KHCO3.
The mass of water needed is 148 - 17.76 = 130.24 g