Answer:
$654
Step-by-step explanation:
Let the amount of money Marlina's received for her salary be x. 
We know that she spent 1/2 of her salary on rent and then $338 on her electric and water bill. So, after this, she will have: 

Left of her salary. 
Next, she spent one half of what was left. So, it will be one-half of the equation. Therefore, she will have spent: 

Finally, she spent $56 for gas. So, we will subtract 56: 

And we know that after all of the expenses, she will have $102 left. Therefore: 

We want to know how much Marlina spent on rent. So, let's find her salary x first. 
First, let's distribute the 1/2: 

Combine like terms: 

Evaluate: 

Add 225 to both sides: 

Multiply both sides by 4: 

Therefore, Marlina received a total of $1308 for her salary. 
We know that she spent half of her salary on rent. Therefore, the amount she spent on rent is: 

And we're done!