Let us have a variable that will hold Jane's age. It will be x.
Then we know Harvey's age is 3x. Because he is 3 times as hold as Jane.
And sum of their ages is 48 years. So we need to add them up together.
x + 3x = 48
Combine like terms.
4x = 48
Divide both sides by 4.
x = 12
We know the age of Jane. And we know Harvey is 36. Because 12 * 3 = 36.