Conditional questions in kobo

Dear Sir,
I created this question in xlx form,

How many people are there in your family?

Suppose the respondent said 10.

If I create such as these questions according to the age category.

How many people are there under age 15?

The respondent said 4

How many people are there under age 35

The respondent said 7

Total 11.

At first he said that we are 10 people in our family.

How can create a condition, in the first total is not equal with the last total, the answer is wrong

Welcome back to the community, @wazir1234! This post discussed previously should help you solve your issue: