I think this is how u ans it , haha.
Not sure if its comp right but im sure u can get method marks T-T
Answer: x=-7/2 y=29/2
Steps:
Use the elimination method
Multiply -3x+y=4 by 5 to make the coefficient next to the y in both equations the same
5(-3x+y=4)
-15x+5y=20
Then, subtract to eliminate the y
-15x+5y=20
- -9x+5y=-1
= -6x=21
Divide both sides by -6 to isolate x
= x= -7/2
Next substitute -7/2 into x in one of the equations
-3(-7/2)+y=4
-21/2+y=4
Add 21/2 from both sides to isolate y
y=29/2
The entire bin can take up to 3/3, meaning, one whole, thus

solve for "x"
Answer:
if your asking about how much he has left it's 20