Mark is six years older than his brother Sam. The sum of their ages is 30. Let a be Sam's age. Set up and solve an equation using the information given to find the value of a.

a = 12 years

Step-by-step explanation:

Mark is 6 years older than his brother Sam. Now, we are asked to represent Sam's age by a. This means that if Sam is a years old, Mark is (a + 6) years old.

The sum of their ages is 30, this means that when we add their ages together, we get the sum of thirty.

Mathematically this means a + a + 6 = 30

2a + 6 = 30

This is the equation needed to get a. To get a, we proceed to solve the equation to completion.

2a = 30 - 6

2a = 24

a = 24/2

a = 12