Pour 1.19 Liters of 12.6 M HCL into 3.81 Liters of water.
The meaning of X Molar concentration is:
The solution has X number of moles of solute per liter of liquid.
For example, the 3.00 M HCl has 3 moles of HCL per liter of liquid.
If you have 5 liters of 3 M HCl, then you have 15 moles of HCL disolved in 5 liters of water.
How much 12.6 M HCL contains 15 moles of HCl?
The rest of the 5 Liters must be water.