Answer: There are 26 trees which they chop down .
Step-by-step explanation:
Since we have given that
the number of trees they chop down is given by

Where 'b' denotes number of hours Ben spends chopping,
'c' denotes number of hours Cam spends chopping,
'j' denotes number of hours Justin spends chopping.
Now, we have also given that,
Number of hours Ben spends chopping = 8
Number of hours Cam spends chopping = 3
Number of hours Justin spends chopping = 4
Now, we put the value of all these variable in the above expression ,we'll get

Hence, there are 26 trees which they chop down .