We assume that the word problem statement contains an error.  We assume that "Amira's age will be one less than thrice Portia's present age." is intended to be "Amira's age will be one less than thrice Elle's present age.".  Otherwise, the problem is not coherent. 

let

x = Almira's present age

y = Elle's present age

Almira's present age is one more than twice the present age of Elle

x = 1 + 2y

if Elle turns 18, Almira's age will be one less than thrice Elle's present age

x + (18 - y) = 3y - 1

by solving the system of equations

x = 1 + 2y

x + (18 - y) = 3y - 1

solve the system of equation

we find

x = 21 years

y = 10 years

Almira is 21 years old now and Portia is 10 years old now.