Answer:
Don has 75 marbles to sell, Mark has 24 marbles to sell
Explanation:
Don has three more than three times the number of marbles Mark has
Now this information can be put into equation form
(In this equation, D = Don and M = Mark)
Equation:
D = 3M + 3
The total number of marbles is 99
This represented as an equation is:
D + M = 99
Now, with both of these equations, it is now a system of equations. Now you must solve the system of equations.
Substitute the value of D from the first equation into the second equation
(3M + 3) + M = 99
4M + 3 = 99
4M = 99 - 3
4M = 96
M = 96/4
M = 24
Now you can substitute the value of M back into the first equation to find the value of D
D = 3(24) + 3
D = 72 + 3
D = 75
This shows that Don has 75 marbles to sell, and Mark has 24.