Answer:
269
Step-by-step explanation:
You want the atomic mass number of an ion with 109 electrons, 159 neutrons, and a +1 charge.
Mass
The +1 charge indicates there is 1 more proton than the number of electrons. The mass number is the sum of the numbers of protons and neutrons:
(109 +1) +159 = 269
The mass number of the ion is 269.
__
Additional comment
The element is Darmstadtium 269, an extremely radioactive isotope of Darmstadtium. Its half-life is 270 microseconds, so there is some contention regarding who first synthesized it. (It is gone before you can claim to have created it.)