The ages of mark and adam add up to 28 years total. mark is 20 years older than adam. how many years old is adam

Let x be the age of Mark, and y be the age of Adam. From the relationships given, we can formulate the following equations:

Eqn 1: x + y = 28

Eqn 2: x = 20 + y

Subsituting Eqn 2 to Eqn 1,

20 + y + y = 28

2y = 28 - 20 = 8

y = 8/2 = 4

Therefore, Adam is 4 years old.