Let C be the age of Carla and M be the age Morgan. Their age today is:
C= 3.M, but 8 years. To find the age of Morgan you have to subtract 8 years from her today's age. Back to the equation C=3.M==>
C-8 = 3(M-8)
18 = 3M - 24 M==> 3M =24+18 ==> 3M = 42 & M= 14, then Carla= 42
