Jim is 3 times as old as his cousin anthony the difference in their age is 18.how old is jim?

Let's create expressions and equations to model this situation. Let Anthony's age be a.

"Jim is 3 times as old as his cousin, Anthony." Jim's age is 3a.
"The difference in their age is 18." 3a - a = 18

How old is Jim?

Let's solve the above equation for a to first find Anthony's age.

    3a - a = 18
    2a = 18
    a = 9

Remember, Jim's age is represented by the expression 3a. Substitute Anthony's age, 9, into the expression to find Jim's age.

    3a
    3(9)
    27

Jim is 27 years old.

The answer is part a: use