Answer:
712
Step-by-step:
First we need to find the total number of small packets:
Anne buys 600(34%)=204 small packets
Ben buys 400(3/10)=120 small packets
Chas buys 210 small packets
Total number of small packets is 204+120+210=534
Now, we know that the number of small packets to the number of medium packets is 3/4, if we let x be the number of medium packets we can write:
3/4=534/x
x=712
:)
