Flight Planning Manual MRJT 1 Figure 4.7.3.;
Normally you would work from DISTANCE to WIND to ALTITUDE to WEIGHT and arrive at the FUEL required. However in this question it is the ALTITUDE that is required.
First, enter at 720nm, to the WIND REF LINE, adjust to 25kt TAIL, then draw a line straight through the ALTITUDE section.
Now enter at 4250kg and work backwards ... across to the 55000kg WEIGHT condition, and then adjust back to the WEIGHT REF LINE.

From this point on the REF LINE, draw a line straight through the ALTITUDE section.
Where the 2 lines meet - read the ALTITUDE - 24000ft...