Answer:
40 minutes
Step-by-step explanation:
Let c represent the number of minutes it would take colleen to finish the job when he is working alone. Hence, it can be represented by the equation:

Solving the quadratic equation to get c gives:
c = -12 and c = 40
Since the time cannot be negative, hence c = 40 minutes.
It would take colleen 40 minutes to clear the yard of leaves alone
Here is the work for that problem
Answer:
d
Step-by-step explanation:
Answer:
u = (-21)/20
Step-by-step explanation:
Solve for u:
u + 1/4 = (-4)/5
Put each term in u + 1/4 over the common denominator 4: u + 1/4 = (4 u)/4 + 1/4:
(4 u)/4 + 1/4 = -4/5
(4 u)/4 + 1/4 = (4 u + 1)/4:
1/4 (4 u + 1) = -4/5
Multiply both sides of (4 u + 1)/4 = (-4)/5 by 4:
(4 (4 u + 1))/4 = (-4)/5×4
4×(-4)/5 = (4 (-4))/5:
(4 (4 u + 1))/4 = (-4×4)/5
(4 (4 u + 1))/4 = 4/4×(4 u + 1) = 4 u + 1:
4 u + 1 = (-4×4)/5
4 (-4) = -16:
4 u + 1 = (-16)/5
Subtract 1 from both sides:
4 u + (1 - 1) = (-16)/5 - 1
1 - 1 = 0:
4 u = (-16)/5 - 1
Put (-16)/5 - 1 over the common denominator 5. (-16)/5 - 1 = (-16)/5 - 5/5:
4 u = (-16)/5 - 5/5
-16/5 - 5/5 = (-16 - 5)/5:
4 u = (-16 - 5)/5
-16 - 5 = -21:
4 u = (-21)/5
Divide both sides by 4:
u = ((-21)/4)/5
5×4 = 20:
Answer: u = (-21)/20