I got x = -78.75 , i included a picture of my work because it’s too difficult to put into text!
3.14 is the square root of pie.
20x-1000 +4000 = 60x
20x-60x= -4000 +1000
-40x= -3000
x= -3000/-40
75 The mix will be 75 lbs
And $20 coffee will be 75 -50 = 25lbs