When Sandy and Allen's mother decorates the house for a holiday by herself, it takes her 5 hours. When both Sandy and Allen help, the three can finish the job in 2.5 hours. When only Allen helps his mother decorate, it takes the two 3.5 hours. How long would it take Sandy to decorate the house by herself?

8 3/4

Step-by-step explanation:

time for all work:

Mother - 5 hours

Mother + Sandy + Allen - 2.5 hours

Mother + Allen - 3.5 hours

Sandy - x

In 1 hour

Mother - 1/5

Mother + Sandy + Allen - 2/5

Mother + Allen - 2/7

Sandy - 1/x

(M+S+A) - S = (M+A)

2/5 - 1/x = 2/7

solve equation

x = 8 3/4 hours

Hope this helps :)

sinn is the total amount of students now and m were the students before, you subtract them both (n-m) and divide that by m. then, since to get a percentage from a fraction you have to multiply by 100, your answer should look like this: n-m/m*100

step-by-step explanation: