Work problems help!!!

A woman can do a certain job in 10 hours and the younger brother can do it in 12 hours. After the woman and her younger daughter havee been working for 1 hour the younger daughter decided to leave the woman doing the job alone.how long did the woman finish the job after the younger daughter left? Pls explain tnx

Rate of woman per hour + Rate of daughter per hour = 1/10 + 1/12 = 22/120 (this means that together they can do 22/120 of the job in an hour)

After an hour, they completed 22/120 of the job. The daughter leaves, so the rate is now 1/10 of the job per hour. Determine how long it will take to finish the job (there's 98/120 remaining):

22/120 + (1/10)x = 1
(1/10)x = 98/120
x = 980/120 = 8.17 hours

Women can complete job in 10 hrs
Daughter(brother) can complete job in 12 hrs
Together they can complete in t where
t/10 + t/12 = 1
12t / 120 + 10t /120 = 1
32t / 120 = 1
t = 120 / 32 = 30/8 = 15/4 = 3 3/4 hrs = 3.75 hrs
In 1 hour they complete
1 / 3.75 x 100%
= 100 / 3.75 %
= 10000 / 375 %
= 2000 / 75 %
= 400 / 15 %
= 80 / 3 %
= 26 2/3 %
Amount of job to be completed
= 100% - 26 2/3%
= 73 1/3%

Now the women will need
73 1/3 % of 10 hrs to complete job

= .73333 x 10

= 7.3333
= 7 1/3 hrs
= 7 hrs 20 mins