Camera = £345
He has already saved £96
He needs £249 (345-96) more. He saves 30% of £80 each week.
30% of 80 is, 80 * 0.3 = £24
At a rate of $24 a week, it will take 10.375 weeks (249/24)
So it will take him 11 whole weeks, or 10.375 weeks to save to be able to buy the camera.