At the very simplest level this is an investigation involving estimation and trial and improvement. The greater depth comes from realising that changing any one corner number affects two others and that this means keeping two conditions in mind simultaneously.

What would be good 'rough' numbers to start with?

When you make this one smaller what happens?

Children can make up their own for others to solve. They could explore the differences between using odd/even numbers in the corners.

Making up questions like these can be a form of support. Start with smaller numbers so that the arithmetic does not get in the way of the thinking.