Answer:
Don has to sell 61 marbles.
Step-by-step explanation:
This question is solved by a system of equations.
I am going to say that:
Don has to sell x marbles.
Mark has to sell y marbles.
The total number of marbles is 75:
This means that:
[tex]x + y = 75[/tex]
Since we want to find x.
[tex]y = 75 - x[/tex]
Don has 5 more than 4 times the number of marbles Mark has
This means that:
[tex]x = 4y + 5[/tex]
Since [tex]y = 75 - x[/tex]
[tex]x = 4(75 - x) + 5[/tex]
[tex]x = 300 - 4x + 5[/tex]
[tex]5x = 305[/tex]
[tex]x = \frac{305}{5}[/tex]
[tex]x = 61[/tex]
Don has to sell 61 marbles.
