from the 1st reaction:
pNOBr / pBr20.5 * pNO = 5.3
from the 2nd reaction:
pN2 * pO2 / pNO2 = 2.1 * 1030
asked: pNOBr2 / pN2 *pO2 * pBr2 = ...
Just substitute the 2nd reaction's Kp equation into the first.
Hint: start by squaring the first reaction's equation.