Amy worked for 5 hours on Saturday so she earned £8 x 5 = £40 on that day.
She earned £130 in total so we know she earned £130 - £40 = £90 working from Monday to Friday.
For every hour Amy worked from Monday to Friday she made £6 so we must divide her total pay by her hourly wage to find the number of hours she worked:
£90/£6 = 15 hours
Amy worked a total of 15 hours from Monday to Friday.