Question

Does anyone know how to do this

Answer 1

Tom's age: x 
Maria is twice as old as Tom sober age is 2x 

2x+x=30

3x=30

x=10 

Tom is 10 years old and Maria is 20 years old.

Answer 2

Maria = x
Tom = y

Use substitution
x+y=30
2y=x

2y+y=30
3y=30
y=10
Tom is 10 years old.

x+y=30

x+10=30
x=20
Maria is 20 years old.