This sample of air at 35°C and 60% relative humidity holds grams/cubic meter of water vapor.

The same sample of air at 40°C can hold a maximum of 50 grams/cubic meter of water vapor. If the air currently holds 30 grams/cubic meter, then its relative humidity is %.

Explanation:

The first part of the text is incomplete but it is not needed to answer the question, which is what is the relative humidity of a sample of air at 40ºC, if it can hold a maximum of 50 grams/cubic meter, and it currently holds 30 grams/cubic meter.

The maximum amount of water that a sample of air can hold  depends on the temperature.

Relative humidity is the percentage ratio of water actually in the air relative to the maximum amount it can hold, at the given temperature.

             = (water in the air) / (maximum amount the air can hold) × 100

It is stated that the maximum amount the sample of air can contain is 50g/m³, and it currently holds 30g/m³, then the relative humidity is: