You need to work out the total number of moles of solute in the two portions of solution, and then divide by the total volume of the two solutions mixed, in order to get the final molarity in mol/l.
Molarity #M = n/V# where n is number of moles of solute and V is volume in litre.
Therefore #n = V.M#
In the first solution, therefore, #n = (130/1000).5 = 0.65# mol.
In the second solution, #n = (170/1000).8 = 1.36# mol
Total number of moles is 0.65 + 1.36 = 2.01 moles. Total volume is 130 + 170 = 300 ml = 0.3 litre.
So final molarity is 2.01 / 0.3 = 6.7 mol/l.