Answer:
The cashier received 100 envelopes
Explanation:
let the number of stamps bought be x.
Cashier will receive 1/3 *x = x/3
Secretary will receive = 1/5 * x = x/5
Now we are told that the secretary received 40 fewer.
This means that the difference between the amounts they received is 40
Mathematically;
x/3 - x/5 = 40
2x/15 = 40
x = (15 * 40)/2 = 600/2 = 300
The cashier received x/3 = 300/3 = 100