Answer:
$872
Step-by-step explanation:
Simple interest = Principle * Rate * Time / 100
= ( 800 * 6 * 18/12 ) / 100
= $ 72
The balance after 18 months = principle + interest
= 800 + 72
= $ 872
should be xy^4/4
next to the last step (x^3(y^3)^4)^1/3
1/x^10
hope that helps:)