Answer:
Let me explain. :)
Explanation:
Step 1:
We know that Gherell has 75 marks. Delia has 5 marks less than Gherell, so we do 75-5 which is 70.
Step 2:
To find out Josiah's mark, we must find 20% of 70. Now, I am not sure if you learned how to find the percents and the amount of decrease, but if you calculate, it is 14. Then you do 70-14 because 14 is how many marks he lost, and that is 54.
Step 3:
Subtract 4 from 54 to get 50 marks.
Step 4:
Shevonne's marks are the average of both Josiah and Liam's mark, so we must find the average. The average is calculated by adding both Josiah and Liam's mark, and divide it by the number of people.

Then, you get 104/2 which is 52. Shevonne has 10 more marks than the average, so you would add 10 to 52 which is 62.
There we have it! Hope it helped. :D