We know that all black beards cost the same money
And all red beards cost $25
And B represents number of black beards
And R represents number of red beards
We have been given the inequality 20B+25R > 350 to show the target for this month.
The above inequality shows that Merlin needs to make more than 350, hence he made 350 last month
Further, it shows that B has been multiplied by 20, hence the black beard's cost was 20