Please answer this math question for me

Combine like terms to make a simpler expression 3z+z

2. explain in words how you plot the point (4, −2) in a rectangular coordinate system.

Avery’s piggy bank has 300 nickels, 450 pennies, and 150 dimes. she randomly picks three coins. each time she picks a coin, she makes a note of it and puts it back into the piggy bank before picking the next coin.