Abigail and Liza work as carpenters for different companies. Abigail earns $20 per hour at her company and Liza earns $25 per hour at her company. Last

week, Abigail and Liza worked for a total of 30 hours and together earned atotal of $690. How many hours did Liza work last week?

Answer as detailed as possible. Thanks :)

L = 18 = hours worked by Lisa

a = 12 = hours worked by Abigail

Step-by-step explanation:

Given the following :

Abigail's earning = $20

Lisa's earning = $25

Last week :

Let number of hours worked by Abigail = a

Number of hours worked by Lisa = L

Total earning = $690

Total hours worked :

a + L = 30 - - - - (1)

To obtain their total earning:

(Lisa's earning per hour * hours worked) + (Abigail's earning per hour * hours worked)). $690

($25 * L) + ($20 * a) = $690

25L + 20a = 690 - - - - (2)

a + L = 30 - - - - (1)

25L + 20a = 690 - - - - (2)

L = 30 - a

25(30 - a) + 20a = 690

750 - 25a + 20a = 690

-5a = 690 - 750

-5a = - 60

a = 12

From (1)

a + L = 30 - - - - (1)

12 + L = 30

L = 30 - 12

L = 18

L = 18 = hours worked by Lisa

a = 12 = hours worked by Abigail

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