Hi,

Let number of non diesel cars be \(x\).

Number of diesel cars= \(54\)

Total number of cars are = \(54 +x\)

Given that 31 of the cars non diesel type are blue so \(x \geq 31\).

Thus minimum number of cars= \(54+31\)= \(85\).

Let number of non diesel cars that are blue = \(y\).

Total number of blue cars = \(31 + y\). Blue cars =\(42\).

So even if total number of cars 180. (54 Diesel 126 Non diesel) no constraints are being violated.

Hence every option Greater than 85 is correct.

Please share the source of the question, because this is particularly peculiar as a GRE question.