In this problem, you don't necessarily need to find the exact values of a and b. Rather, find the value of (a+b) first, and then you can substitute it into the next equation. First, you can divide both sides of the first equation 2(a+b)= -8.1 by 2, to get (a+b)=-4.05. Now, subsitute the value of (a+b) into the second equation, -0.5(a+b), to get -0.5(-4.05). From here, you can calculate that -0.5 times -4.05 is 2.025. Hope this helped!
