What volume of a 750M NH4C2H3O2 ammonium acetate must be add

What volume of a 7.50M NH4C2H3O2 (ammonium acetate) must be added to make 250.0mL of a 3.95M solution?

The following formula can be used

Va x Na = Vb x Nb

Va = 250 ml Na = 3.95 M

Vb = ? Nb = 7.5 M

Substitute the values and calculate Nb

Nb = 250 x 3.95 / 7.5 = 131.66 ml

Hence 131.66 ml is needed to make up