Step 1 :First, we need to find the total number of orders from all restaurants. This is done by adding the number of orders from each restaurant. In this case, we have \(324 + 34\) orders from Restaurant A, \(266 + 59\) orders from Restaurant B, \(236 + 35\) orders from Restaurant C, and \(122 + 20\) orders from Restaurant D. This gives us a total of \(1096\) orders.
Step 2 :Next, we need to find the number of ways to select three orders from Restaurant A. This is given as \(45498936\).
Step 3 :Finally, we can find the probability by dividing the number of ways to select three orders from Restaurant A by the total number of orders. This gives us a probability of approximately \(0.0346544687395977\).
Step 4 :\(\boxed{0.0347}\) is the final answer, which represents the probability that all three orders are from Restaurant A.