A man's age is 20% more than that of his sister.find the sister's age if the man is 42 years old.

1.2x = 42

Solve for x.

35 To find the sister's age, we can use the information that the man's age is 20% more than his sister's age. Let's call the sister's age "x".

According to the information given, the man's age is 20% more than his sister's age, which can be expressed as:

Man's age = Sister's age + (20% of Sister's age)

We know that the man's age is 42 years old. So we can now substitute the values into the equation:

42 = x + 0.2x

Now, let's simplify the equation:

42 = 1.2x

To isolate x, divide both sides of the equation by 1.2:

42/1.2 = x

35 = x

Therefore, the sister's age is 35 years old.