Steven has identical twin sisters who were born only five minutes apart. Steven is 12 years old. If the combined ages of Steven and his twin sisters equal 42 years, how old are his sisters? Part One: Select the equation that should be used to solve this question correctly. Steven is 12 years old. If the combined ages of Steven and his twin sisters equal 42 years, how old are his sisters? Part Two: Use the equation you selected in Part One find out the age of sisters. Write only a number or numbers as your answer.