Can i get help here ?

It will be 10z-30
Because you are collecting like terms with -5z and +5z and it will give you 10z and 30 will be by it’s self because it has nothing to add or subtract with .

Rounding decimals is very similar to rounding other numbers. if the hundredths and thousandths places of a decimal is forty-nine or less, they are dropped and the tenths place does not change. for example, rounding 0.843 to the nearest tenth would give 0.8. , your welcome !