Answer:
Harry has a score of 30
Explanation:
Let us represent their scores as:
Nathan = x
Harry = y
Jack = z
At the end of a football season a coach is adding up everyone's scores
Nathan has scored 11 more than harry
x = y + 11
Harry has scored 10 more then jack.
y = z + 10
z = y - 10
If the total of their scores is 91
x + y+ z = 91
y + 11 + y + y - 10 = 91
3y + 1 = 91
3y = 91 - 1
3y = 90
y = 90/3
y = 30
Since Harry's score is represented as y, Harry has a score of 30