Yashvi

Hi, I apologise if this is not the right place to ask but I'm confused regarding tax. I have been working in a flexible part time job (let's call it Job A) as a student which paid me 11.83 per hour and was roughly between 10 to 15 hours a week. Now that I've completed studies I have just started a second part time job (Job B) which is a fixed 22 hour per week contract, paying 11.75 per hour. My confusion here is since Job A is very subjective I don't have an estimate of how much I can earn from it. But I believe combining both I can earn somewhere between 1200 to 1500 per month, (if i get the hours) which is more than monthly cut off for personal allowance, I believe. I guess what I'm trying to ask is how would all this affect my tax code going forward. Would I be charged 20% of tax at only job B when both job A and B combined is more than allowance? And if so, is there any option to request to get taxed for Job A rather than Job B; As Job B is currently the source of stable income for me. Thank you for your help.