Answer:
$336
Explanation:
When Lilian works 7 hours a day for 5 days in a week, she earns $420.
When she works 7 hours a day for 4 days a week , her weekly earnings are reduced by 20%.
This means that her new earning is 80% of her prior earning.
Lilian's new earning =
![\[(80)/(100)*420\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/be9oida0unf0e52uuz86jdnaxa0m8glti5.png)
=
![\[(33600)/(100)\]](https://img.qammunity.org/2021/formulas/mathematics/high-school/7335mcotua4myhout8eupki8a5x0loaucp.png)
=

Hence the new weekly earning of Lilian is $336.