It appears that you issue is setting up the equations to solve. I will not be giving the full solution however I will slowly guide you through.
To start off we will call the hourly rate of last week x.
So last week she earn $x an hour. We do not know what x is.
Now. This week she earnt 0.75 more.
So what is 0.75 more than x?
Now just to make sure you understand this first part. Say she got a demotion and earnt $0.50 less per hour. What would her pay be then?
And how about if she earn 1.5 times as much?
And lastly what if her pay rise was $y more an hour?
Hopefully you get this concept now. It is fundamental in solving maths problems whether is is for differential equations, area or money.
Now wee need to work out her total earnings for the week.
Week 1 she worked for 18 hours. So how much did she earn? Well you know her hourly rate (x) and how many hours she worked so last week she earnt $18x.
Now we need to do the same for this week. This one is slightly more complicated but it works the same way. She worked 14hours at a rate of ($x+0.75) an hour. So the total amount earnt for the week was the numbers of hours times the rate per hour.
Cannyou work that one out?
It is Really the same logic.
Not we need to do something about these. Well the total pay is this week's pay plus last week's pay. We know the total pay and how much she earnt this week and last week in terms of x.
So can you make an equation for this?
Now solve that equation for x and then add 0.75 for this week.
Hopefully you can do that