15 points
pls help fast with all questions
thank you

11a

11b

12

Anna is 18. Rita is 13.

13

Mark is 12.

Step-by-step explanation:

Recall that the perimeter of a shape is the sum (or total) of all the edges that make up that shape. So, for the first shape, there are three Xs. We write this as so this is the perimeter.

In the second, there are four Xs, so this is .

In the third, there are two Xs and two 5s, so this is .

In the fourth, there are two Xs and three 4s, so this is .

If each is equal to 24, we can simply set them as equal to 24 and solve.

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If Anna is 5 years older than Rita, then . If their sum is 31, then . We can perform some substitution:

Therefore, Rita is 13. Keep going:

Anna is 18.

If Dad is three times as old as Mark, then . If the sum of their ages is 48, then . We can perform some algebra:

Dad is 36. Keep going:

Mark is 12.

Now that you've seen these, you do the bonus ;)