It should be a moment\textquotesingle s work to see that Felix weighs $$3\text{kg}$$ , and Marmalade $$7\text{kg}$$ . 
Felix and Marmalade are two cats. Together they weigh $$10\text{kg}$$.  Felix weighs $$4\text{kg}$$ less than Marmalade. How much does Marmalade weigh? 
$$3\text{kg}$$ 
$$6\text{kg}$$ 
$$7 \text{kg}$$ 
$$9\text{kg}$$ 
$$14 \text{kg}$$ 