posted by Brittany .
Luis is 10 years older than his brother. Next year, he will be three times as old as his brother. If the brother's age is represented by a, what is Luis' age? What will be the brother's age next year?
Luis = a + 10
Luis + 1 = 3a
Substitute a+10 for a in second equation and solve for a. Insert that value into the first equation and solve for Luis. Check by inserting both values into the second equation.