Table 2.2.3 .... there are 3 parts to the table ... in terms of Temperature condition, the table gives 'ISA Deviation' ... 'ISA -20ºC'. ISA, and 'ISA +20º'.

So, for this question we are at FL 75, ISA at this level is 0ºC, so with OAT +10ºC, we are 10ºC warmer than ISA, so the ISA Deviation is 'ISA +10ºC' ..... therefore, to answer the question, we need to interpolate between the 'ISA' and 'ISA +20ºC' sections of the table.