What does it mean can anyone and give an example in number one

So there are a list of significant figures rules that, to be completely honest, are just much easier to have memorized so that you know them in the future.

Attached is a few rules with a link to a helpful webpage on the rules.

So for example in number 1, we need to change 22.60 m to 2 significant figures.

We know that the number we have is actually 4 significant figures, because the zeros after the decimal are considered significant. And we know that the 6 is also considered significant. So we are going to have to cut those 2 digits away from the number. So we have a leading '22' in front of the decimal. Since these are the 2 significant figures we are going to keep, we are then going to round up to 23 due to the number after the decimal being '0.6' (0.5 or higher, you round up to the next number).

So then the answer for number 1 will be 23 m.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.