Verbal Reasoning Q = beyond me

[lola38]

My DS is sitting a verbal test end Jan, he asked my help with

5 (15) 2 7 (5) 6 4 ( ?) 3

Anyone who is good at this pls ?

5

(5 - 2) x 5 = 15
(7 - 6) x 5 = 5
(4 - 3) x 5 = 5

Thank you

Ah Type 19 VR - my favourite

I see what prh has done, but how does anyone know what the brackets are for?

In the question it is just a way of showing that the number in the middle is somehow calculated from the numbers either side. No deeper meaning than that.