What volume 12.6 m hcl must be added to enough water to prepare 5.00 litters of 3.00 m hcl?

To solve this problem, we shall use the role;
M1V1 = M2V2
M1: is the molarity of the solution before dilution.
V1: is the volume of the solution that we need to dilute.
M2: is the molarity of the solution after dilution.
V2: is the volume of the solution after dilution.

By substitution;
12*V1 = 3*5
V1 = 1.25 litters.