Answer:
It would take 25 minutes for Patrick to complete the project alone.
Step-by-step explanation:
They did the project in 20 minutes, that is, 100% of the project, so:

In which x is the percentage that Patrick worked and y is the percentage that Stewart worked.
Patrick works four times as quickly as Stewart, so x = 4y.
So




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Patrick did 80% of the project in 20 minutes. We can solve this problem by a simple rule of three, in which the time it would take for him to complete the project alone is 100%. So
20 minutes - 0.8
x minutes - 1


It would take 25 minutes for Patrick to complete the project alone.