Answer:
1) C. x = 3y
D. x - y = 10
2) Brit is 15 years old.
3) Tyrese is 5 years old.
Explanation:
Part 1
Given information:
- Brit is 10 years older than her brother Tyrese.
- Brit is 3 times as old as Tyrese.
Let "x" be Brit's age (in years).
Let "y" be Tyrese's age (in years).
If Brit is 10 years older than her brother Tyrese, then if we subtract Tyrese's age from Brit's age, we get 10. Therefore, the equation that models this is:

If Brit is 3 times as old as Tyrese, then the equation that models this is:


Part 2
We now have a system of linear equations:

To solve the equation for x (Brit's age), rewrite the first equation to isolate y:

Substitute the found expression for y into the second equation, then solve for x:

Therefore, Brit is 15 years old.

Part 2
To find Tyrese's age, substitute the found value of x into the rearranged first equation and solve for y:

Therefore, Tyrese is 5 years old.