Jo makes 170 minutes call. There are 150 free ones
170 - 150 = 20
20 minutes are "what Jo has to pay"
Jo sends 182 texts. There are 150 free ones
182 - 150 = 32
32 texts are "what Jo has to pay"
Monthly charge = 16p, 13p for each extra minute, 15p for each extra text.
13(20) = 260p
15(32) = 480p
480p + 260p + 16 = 740p + 16
740p + 16 is your answer (if p = pounds, add 16 to it, i'm not sure what p stands for though. If it is cents, divide 100 from 740 and take out the p, then add total to 16 to get answer.)
hope this helps