Answer:
Sally is 23 years old.
Explanation:
John's age is completely unknown, so it is known as x
Meanwhile, Sally's age can be represented as 3x+2
The sum of both ages is 30.
So, x+3x+2=30
Combine like terms.
4x+2=30
Subtract 2 from both sides.
4x=28
Divide both sides by 4.
x=7
John is 7 years old.
Sally's age: 3(7)+2=23
Sally is 23 years old.