What does the little 2 in 202 mean

Which best explains why an iceberg floats?

Imagine that twenty i.u.’s of enzyme z were catalyzing the above reaction for one minute, under vmaxconditions, in a 3.00 ml assay volume. the assay is buffered with 20 mm phosphate buffer, ph 7.60. what will the ph be at the end of that one minute?

The diagram below shows the different phase transitions that occur in matter. which arrow represents the transition in which dew is formed?