Question 201720
Let L = Louise' present age and S = Sue's present age.
1) S = 7*L  "Sue is now seven times as old as Louise."
2) S+6 = 5(L+6) "In six years Sue will be five times as old as Louise (will be in six years)"
Substitute S = 7*L from equation 1) into equation 2) and solve for L.
2a) 7*L+6 = 5(L+6) Simplify.
2a) 7L+6 = 5L+30 Subtract 5L from both sides.
2a) 2L+6 = 30 Subtract 6 from both sides.
2a) 2L = 24 Divide both sides by 2
2a) L = 12 and S = 7*L = 7*12 = 84
Louise is 12 years old and Sue is 84 years old.