Step-by-step explanation:
Assuming the information in the question is
30 protons, 26 electrons
12 protons, 11 electrons
10 protons, 10 electrons
17 protons, 10 electrons.
(But if it's not, it's not a big deal... the concept is pretty simple once you understand it. :) )
Each proton is worth (+1) charge. Each electron is worth (-1) charge. Basically, you get +1 point if you have a proton, you lose -1 point if you have an electron.
Case 1: 30 protons, 26 electrons
+30 - 26 = +4
The overall charge is +4.
Case 2: 12 protons, 11 electrons
+12 - 11 = +1
The overall charge is +1.
Case 3: 10 protons, 10 electrons
+10 - 10 = 0
The overall charge is 0 (or neutral).
Case 4: 17 protons, 10 electrons
+17 - 10 = +7
The overal charge is +7.