I've done the whole exercie of worded questions but I'm struggling with these two.

6. In four years time a mother will be three times as old as her son. Four years ago she was five times as old as her son. Find their present ages.

8. Two children had 110 marbles between them. After one child had lost half her marbles and the other had lost 20 they had an dqual number. How many marbles did each child start with and how many did they finish with?

I can do it with trial and error but it'd be much more helpful in algebraic terms as this is an algebra topic.