Add 1.3ml of 72 mg/ml to 8.7ml 3mg/ml to give 12mg/ml
[1.3ml x72mg/ml = 93.6 mg nic, 8.7ml x 3mg/ml = 26.1 mg nic, total volume = 10ml, therefore you have 119.7 mg nic in 10ml, or 12mg/ml which is 1.2% nic] you will of course lose some flavour due to the dilution.