Answer:
Mary: 16
Kevin: 22
Ahmed: 88
Step-by-step explanation:
This could be written as the following formula.
Mary + Kevin + Ahmad = 126
and we know that
Mary + 6 = Kevin
Kevin * 4 = Ahmed
so Ahmed = (Mary + 6) * 4
When filling this in you get
Mary + Mary + 6 + (Mary + 6) * 4 = 126
Mary + Mary + 6 + 4Mary + 24 = 126
6Mary + 30 = 126
6Mary = 96
Mary = 16
So Mary served 16 orders.
Using the earlier formulas you get
Kevin = Mary + 6 = 16 + 6 = 22
Ahmed = Kevin * 4 = 22 * 4 = 88.
Now we just need to double check it.
Mary + Kevin + Ahmad = 16 + 22 + 88 = 126. Which matches what it should be.