Question

Tyler is three-fourths of his brother's age. The sum of their ages is 21. How old is Tyler?

Answer 1

21=x+3/4x (x=brother's age)
To solve this you would need to use the equation above.
Tyler would be 9 years old and his brother would be 12.
21=12+9
21=21
The correct answer is 9. 

Answer 2

Answer:

Tyler is three-fourths of his brother's age. The sum of their ages is 21. How old is Tyler?

Tyler is 9 years old