Need on number 18 and 19 ! i start school !

Plz me i need i will give a brain

If the measure of xyz is 81 what is the measure of yz

Helll ! 1,400 tons of wheat of two different varieties was delivered to the silo. when processing one variety, there was 2% of waste and 3% during the processing of the second variety of wheat. after the processing, the amount of remaining wheat was 1,364 tons. how many tons of each variety of wheat was delivered to the silo?