Question 8276
Let T = Tony's age now and B = his brother's age now.

T = B + 6  Tony is 6 years older than his brother.
T - 4 = 2(B - 4) Tony's age 4 years ago (T-4) was twice his brother's age (2(B-4))

Substitute T = B + 6 into the second equation, simplify and solve for B.

(B + 6)-4 = 2(B - 4)
B + 2 = 2B - 8 Subtract B from both sides.
2 = B - 8 Add 8 to both sides.
B = 10 His brother's age is 10 years.
T = B + 6 = 10 + 6 = 16 Tony's age is 16 years.