Answer:
Ziad is 30 years old.
Marc is 10 years old.
Step-by-step explanation:
We will use m to represent Marc's age this year, and z to represent Ziad's age this year.
This year:
z = 3m
To show their relative ages in ten years time:
z + 10 = 2(m+10)
We can rearrange this to make m the subject.
z + 10 = 2m + 20
z = 2m + 10
We also know that m = 3z. We can substitute this value into our equation.
3m = 2m + 10
m = 10
Use z = 3m to find that z = 30.