change the first equation so that the two equations look similar
isolate z... so from 5j+z=3 , you will have z=3-5j
then multiply from both sides by 2
you should get 2z=6-10j
the second equation is 2z=a -bj
you can now see the relation: a=6 while b=10
a+b= 6+10= 16
Hope this helps!
