<u>Answer:</u>
Mitch has taken 17 complete lesson and 60% of one last lesson.
<u>Solution:
</u>
Dan and Laura needs to pay certain amount for swimming lessons.
Dan took four lessons and paid $ 100
Laura took 8 lessons and paid $ 200.
Need to calculate number of lessons taken by Mitch when amount paid by Mitch = $440.
Let’s first calculate price of one lesson.
For 4 lessons of Dan, payment = $100
So for 1 lesson of Dan, payment 
For 8 lessons of Laura, payment made = $200
So for 1 lesson of laura, payment made = 
So clearly cost of 1 lesson = $ 25.
So <em>number of lessons taken by Mitch</em> = Amount spent / cost of 1 lesson

So Mitch has taken 17 complete lesson and 60% of one last lesson.