The correct answer is 68.

Solution:

Considering the given number pattern.

Here, the numbers are decreasing.
So, to find the missing number, we first find the rule.

Note that:
98 - 10 = 88
88 - 10 = 78
78 - 10 = 68
68 - 10 = 58

So, the rule is "subtract 10".

Then, the missing number is 68.